Longitudinal Reinforcement Ratio Research Articles

Experimental and numerical analyses of the effect of fibre content on the close-in blast performance of a UHPFRC beam

Limited research has been conducted on the influences of fiber content on close-in blasting characteristics for ultrahigh-performance fiber-reinforced concrete (UHPFRC) beams. This paper aims to address this knowledge gap through experimental and mesoscale numerical methods. Experiments were conducted on ten UHPFRC beams built with varying steel fiber volumetric fractions subjected to close-in explosive conditions. Additionally, this study considered other parameters, such as the longitudinal reinforcement type and ratio. In the case of UHPFRC beams featuring normal-strength longitudinal reinforcement of diameters Φ12, Φ16, and Φ20, a reduction in maximum displacement by magnitudes of 19.6%, 19.5%, and 17.4% was observed, respectively, as the volumetric fractions of fiber increased from 1.0% to 2.5%. In addition, increasing the longitudinal reinforcement ratio and using high-strength steel longitudinal reinforcement both significantly reduced the deformation characteristics and increase the blasting resistances of UHPFRC beams. However, the effects on the local crushing and spalling damage were not significant. A mesoscale finite element model, which considers the impacts of fiber parameters on UHPFRC beam behaviors, was also established and well correlated with the test findings. Nevertheless, parametric analyses were further conducted to examine the impacts of the steel fiber content and length and the hybrid effects of various types of microfibers and steel fibers on the blasting performance of UHPFRC beams.

Flexural performance tests and machine learning analysis of prestressed high strength steel reinforced concrete beams

ABSTRACT This paper reports a study on the flexural performance of prestressed high strength steel reinforced concrete (PHSSRC) beams and proposes machine learning (ML) models for predicting the flexural bearing capacity of steel reinforced concrete (SRC) beams. Seven prestressed steel reinforced concrete (PSRC) beams were tested under a four-point bending load to investigate the effect of steel strength grade, steel ratio, and longitudinal reinforcement ratio on the flexural load capacity of beams. The test results indicated that increasing the steel strength grade and steel ratio significantly enhanced the bearing capacity of PSRC beams. A database consisting of 112 sets of experimental data on the flexural performance of SRC beams, including the test data in this study, was established for training and validating the ML models. Artificial Neural Network (ANN) model and eXtreme Gradient Boosting (XGBoost) model were respectively developed to predict the flexural load capacity of SRC beams, and the accuracy of the flexural load capacity values predicted by the design specification, the ANN model and the XGBoost model were compared. The results show that the XGBoost model has the best prediction performance. Finally, the sensitivity analysis of the parameters was performed using the Shapley Additivity (SHAP) interpretation method.

Shear strength assessment of reinforced recycled aggregate concrete beams without stirrups using soft computing techniques

This paper presents a study to predict the shear strength of reinforced recycled aggregate concrete beams without stirrups using soft computing techniques. The methodology involves the development of a Multi-Objective Genetic Algorithm Evolutionary Polynomial Regression (MOGA-EPR) and Gene Expression Programming (GEP) models. The input variables considered are the longitudinal reinforcement ratio, recycled coarse aggregate ratio, beam cross-section dimensions, and concrete compressive strength. Data collected from the literature were used to train and validate the models. The results showed that the MOGA-EPR and GEP models can accurately predict the shear strength of beams without stirrups. The models also performed better than equations from the codes and literature. This study provides an alternative approach to accurately predict the shear strength of reinforced recycled aggregate concrete beams without stirrups.

Stress-strain behavior of columns confined with bamboo reinforced concrete jacket

ABSTRACT The need for retrofitting of building structures is generally caused by two cases: to repair damaged structures or to improve the structural performance of weak structures. The concrete jacket method is widely chosen to solve the problem due to the more economical and simple procedure compared to other methods. In this study, retrofitting using bamboo-reinforced concrete jacket (BRCJ) was applied on reinforced concrete columns. Bamboo was used to replace steel as the longitudinal and transverse reinforcements of the concrete jacket with the aim of finding an alternative for an environmentally friendly green material and a lower-cost manufacturing process compared to steel. The performance of the jacket was studied by investigating the confinement effectiveness that is influenced by initial column conditions, spacing of bamboo stirrups, and the slenderness of longitudinal reinforcement. The outcomes showed that the bamboo-reinforced concrete jackets were able to strengthen the columns up to 170% and 140% of the initial strength of the undamaged and damaged columns, respectively. The BRCJ is more effective on columns that are still at the pre-peak-strength stage. The confinement effectiveness is also largely affected by the bamboo stirrups spacing. By reducing the spacing of bamboo stirrups to about half that of steel stirrups, the ductility ratio of retrofitted columns increased up to 90% higher than the original columns. Further, the confinement effect of BRCJ can also be increased by increasing the slenderness ratio of bamboo longitudinal reinforcement. Finally, the stress–strain relationship for concrete columns retrofitted with bamboo-reinforced concrete jackets has been proposed which shows great agreement with the experimental data. Overall, BRCJ has shown promising results to be used to strengthen damaged or weak structures.

Effect of tie column on the progressive collapse performance of infilled reinforced concrete frames

In practice, reinforced concrete (RC) infilled frames having longer span are provided with tie columns to improve structural integrity but previous work ignored tie columns in studying the effect of masonry infills on progressive collapse resistance of RC frames. Therefore, aim of this study is to explore the effect of tie columns on the progressive collapse resistance of RC infilled frames under column removal scenarios. The high-fidelity-based finite element model of RC infilled frames were first developed and validated with published experimental results. The validated model was then further evolved to an RC infilled frame having tie columns to evaluate the influence of tie columns on the load transfer mechanism and the resistance of the RC infilled frame against progressive collapse. Thereafter, the numerical model was further utilized to study the effects of the pertinent parameters, including the number of stories, the span length of the frame and the longitudinal reinforcement ratio of the tie columns. Finally, equivalent strut model was suggested for macro-modeling of RC infilled frames having tie columns in engineering practice. The results showed that incorporating tie columns makes truss mechanism more fully mobilized in masonry infill walls and the inclined angles of primary struts in each sub-panel of the infill wall are increased, improving the vertical components of diagonal compression in resisting the gravity load. Consequently, introducing tie columns at middle span of infill wall panels helped to increase the initial stiffness (about 19%), peak resistance (about 26%) and post-peak resistance of RC infilled frame under a middle column removal scenario. Such beneficial effect of tie columns becomes more significant for infilled frames with larger spans, and the longitudinal reinforcement ratio of tie columns should be ≤ 0.24%.

Behavior of non-prismatic RC beams with conventional steel and green GFRP rebars for sustainable infrastructure

This study presents an experimental and finite element analysis of reinforced concrete beams with solid, hollow, prismatic, or non-prismatic sections. In the first part, a total of six beams were tested under four-point monotonic bending. The test matrix was designed to provide a comparison of structural behavior between prismatic solid and hollow section beams, prismatic solid and non-prismatic solid section beams, and prismatic hollow and non-prismatic hollow section beams. The intensity of shear was maximum in the case of prismatic section beams. The inclusion of a tapered section lowered the demand for shear. In the second part, Nonlinear Finite Element Modeling was performed by using ATENA. The adopted modeling strategy resulted in close agreement with experimental crack patterns at ultimate failure. However, the ultimate failure loads predicted by nonlinear modeling were generally higher than their corresponding experimental results. Whereas in the last part, the developed models were further extended to investigate the effect of the strength of concrete and ratio of longitudinal steel bars on the ultimate load-carrying capacity and cracking behavior of the reinforced concrete beams with solid, hollow, prismatic, or non-prismatic sections. The ultimate loads for each beam predicted by the model were found to be in close agreement with experimental results. Nonlinear modeling was further extended to assess the effects of concrete strength and longitudinal reinforcement ratio on failure patterns and ultimate loads. The parametric study involved beams reinforced with glass fiber-reinforced polymer (GFRP) bars against shear and flexural failure. In terms of ultimate load capacities, diagonal cracking, and flexural cracking, beams strengthened with GFRP bars demonstrated comparable performance to the beams strengthened with steel bars.

Experimental and numerical studies of circular precast concrete slender columns with intermediate connection filled with high-performance concrete

Precast concrete (PC) slender columns with intermediate connections are often used in building construction. However, no studies have been performed on the behavior of PC slender columns with intermediate connections filled with high-performance concrete namely engineering cementitious composites (ECC) and strain hardening cementitious composites (SHCC). This paper presents the testing and computer modeling of axially loaded PC slender columns with splices filled with ECC and SHCC. Experimental program and results are presented on nineteen PC slender columns under concentric compressive load up to collapse. The test parameters include the longitudinal reinforcement (µ) ratio, and embedded length of steel bars/infilled concrete connection (Le). Three different reinforcement ratios of 0.027, 0.031, and 0.036 are considered. The embedded length of steel bars/intermediate concrete connection varies from 15D, 22.5D, and 30D where D is the bar diameter. Experimental results indicate that the use of longer steel bars/intermediate concrete connection and a higher reinforcement ratio can significantly enhance both the cracking and ultimate loads of PC slender columns with an intermediate concrete connection. The elastic stiffness of the PC slender columns with ECC and SHCC connection is found to increase by 150% and 93%, respectively when compared to the control specimen. Similarly, filling the splice of the PC columns with ECC and SHCC improves the energy absorption capacity by 107% and 138%, respectively. Nonlinear three-dimensional finite element models (FEMs) are developed accounting for the initial imperfection of the slender columns and their accuracy is validated by experimental results. It is shown that the FEM can provide an accurate simulation of the performance of PC columns with splice connection.

Flexural behaviour of hollow reinforced concrete T-beams strengthened or retrofitted with carbon-fibre-reinforced laminates: Experimental and numerical investigation

This study investigates the effect of longitudinal rectangular openings on the flexural behaviour of reinforced concrete (RC) T-beams strengthened or retrofitted with external carbon-fibre-reinforced polymer (CFRP) laminates. Eight RC T-beams, with one solid and one hollow beam in each of four groups, were analysed using a three-point bending test. The CFRP laminate used in each beam was similar, and the beams had an identical longitudinal reinforcement ratio. The ultimate load capacity of the strengthened hollow RC T-beams showed a 9% decrease compared to that of the strengthened solid RC T-beams, while retrofitted hollow RC T-beams with 100% preloading exhibited a 24% decrease in ultimate load capacity compared to that of retrofitted solid RC T-beams. In addition, the CFRP laminate had a positive effect on reducing strain in hollow RC T-beams as compared to that of solid RC T-beams. The flexural behaviour of the CFRP-strengthened hollow RC T-beams with a 5% cross-sectional hollow core area was similar to that of strengthened solid RC T-beams. However, after preloading, the retrofitted hollow RC T-beams exhibited a decrease in flexural efficiency compared to the retrofitted solid beams. A validated numerical model was developed using ABAQUS to accurately simulate the behaviour of the hollow RC T-beams. Subsequently, a parametric study was conducted using the validated model to investigate the effects of varying the position and size of the hollow section on the response of the RC T-beams.

Probabilistic curvature-and-drift limit states predictive models of high-strength bridge columns

This study presents the derivation of closed-form component limit state expressions for high-strength concrete columns reinforced with high-strength steel bars (HSC-HSSB) from an extensive database through the moment–curvature analysis approach. Initially, sensitivity analysis was conducted to investigate the regularity of the parameters (section size, axial-load ratio, longitudinal reinforcement ratio, stirrup reinforcement ratio, concrete compressive strength, and yield strength of longitudinal reinforcement) on the curvature limit state. The approach being convenient, massive samples were obtained in a short time, therefore, 6^7(279936) levels were generated to derive the predictive expressions of curvature and moment limit states by using the logarithm linearity model. Subsequently, based on the cross-section expressions, the drift displacement and shear force limit states predictive expressions were derived and verified by experimental studies, and these limit states were predicted with high precision. Moreover, after considering the uncertainty of material and section size, the curvature and drift displacement of the HSC-HSSB column exhibited a lognormal distribution, and the useful suggested standard deviations (βc) in different limit states were proposed for practical application of fragility curves to assess the vulnerability of bridge columns to earthquakes.

Experimental and Numerical Investigations of the Seismic Performance of Railway Gravity Piers with Low Reinforcement Ratios

Gravity pier is a widely employed pier type in railway bridges worldwide. It is characterized by a solid cross-section with a low longitudinal reinforcement ratio which can be even lower than 0.5%. These low-reinforced gravity piers have been found to be vulnerable under major earthquakes, but their seismic performance has not been fully understood. Improving the seismic safety of these piers and reducing the consumption of reinforcing steels coincide with multiple Sustainable Development Goals (SDG 6, 7, and 9). In this concern, three main objectives are achieved in the present research. Firstly, quasi-static tests were conducted on two gravity piers with low longitudinal reinforcement ratios: 0.3% and 0.4%. The tests found the reinforcement ratio significantly affected the failure mode and seismic capacity. A typical brittle failure was observed in the specimen with the 0.3% reinforcement ratio. Fracture of longitudinal reinforcing steels was heard, and only a few cracks formed within a narrow region at the pier bottom, whereas the structural behavior of the specimen with a 0.4% reinforcement ratio was ductile, and cracks were located within a wider region (800 mm) at the pier bottom. Increasing the reinforcement ratio significantly increased the energy dissipation capacity and the displacement ductility. Secondly, finite element models of two specimens built using ANSYS were validated with test results, and then a series of finite element models were built to further investigate the influences of three important parameters on the seismic capacity. The three parameters are shear span to depth ratio, axial compression ratio, and longitudinal reinforcement ratio. The validations found that the load–displacement hysteretic curves and the distributions of concrete plastic strain from finite element analyses matched well with those from tests. Further finite element analyses found that the shear span to depth ratio was inversely correlated with the peak lateral load, but positively correlated with the displacement ductility. Conversely, increasing the axial compression ratio increased the peak lateral load but decreased the displacement ductility. Thirdly, an analytical equation was proposed to predict the displacement ductility of low-reinforced gravity piers, and the predicted ductilities agreed well with those obtained from finite element analyses. The findings provide a better understanding of the seismic performance of low-reinforced gravity piers, which helps extend the application of these piers. Furthermore, the proposed analytical equation assists in the evaluation and design of these piers.

Seismic behavior of steel-reinforced high-strength concrete composite beams with bonded tendons

To study the seismic behavior of steel-reinforced high-strength concrete composite beams with bonded tendons (PSRHSCBs) under low cyclic loading, 13 PSRHSCBs were designed with the main parameters of the span-to-height ratio of beams (L/H), the cubic strength of concrete (fcu), the eccentricity of H-shaped steel (eH), the volume stirrup ratio (pv), the longitudinal reinforcement ratio (p), and the tension control stress of tendons(σcon). Using the simplified bilinear constitutive model of steel and the nonlinear constitutive model of high-strength concrete, and introducing plastic damage of concrete, fine finite element models were established with ABAQUS software. 11 similar test specimens were conducted by above modeling method, by comparing existing test curves and numerical simulation curves, both of them match well, which verified the validity of the modeling method. Subsequently, parameter analysis for 13 PSRHSCB specimens was performed, and the influence regularity of different parameters on the seismic behavior of this kind of composite beams was obtained. The results show that hysteretic curves of this kind of composite beams are full, and the failure mode is manifested as bending failure. The ultimate load, the energy dissipation capacity and the ductility coefficient of specimens can be improved significantly by increasing pv, on the contrary, the energy dissipation capacity and the ductility coefficient decrease gradually by increasing fcu. The stiffness degradation of specimens significantly slows down with the increasing of L/H and σcon, and the decreasing of eH. Finally, the trilinear skeleton curve model and the restoring force model are established by statistical regression, and the corresponding seismic design suggestions are given, and these can provide theoretical support for the seismic design of such composite beams in actual engineering.

Influence of concrete and unbonded ratio on RC beams

Hybrid aggregates, comprising normal-weight and lightweight aggregates, offer an effective means to enhance the physical and mechanical properties of concrete. However, the comprehensive effect of hybrid aggregate concrete on the flexural performance of reinforced concrete (RC) beams remains largely unexplored. In this study, utilizing LC30 lightweight concrete, LC40 gravel lightweight concrete, hybrid aggregate lightweight concrete, and hybrid aggregate concrete with reduced ceramsite content as matrix materials, RC ordinary beams and RC bond-slip beams with dimensions of 150 mm × 300 mm × 2400 mm were meticulously designed and fabricated. Employing a four-point bending test, the effects of the concrete matrix, the unbonded ratio, and the reinforcement ratio of the bottom longitudinal rebar on the flexural behavior of the two types of beams were scrutinized. Furthermore, the load–deflection and load–slip responses were subjected to numerical simulation using the finite element method. The findings demonstrate that hybrid aggregates exert a substantial influence on adjusting the dry apparent density, strength, and elastic modulus of concrete to align with design specifications. While the physical and mechanical characteristics of both beam types are primarily governed by the reinforcement ratio and unbonded ratio, the concrete matrix, despite its distinct properties, exhibits minimal effect on these attributes. Nevertheless, it significantly affects beam stiffness and the relative slip between the rebar and the concrete matrix. Both beam categories adhere to the plane section assumption and reveal that optimal collaborative performance between the rebar and concrete matrix occurs at a bottom longitudinal reinforcement ratio of 1%, albeit diminishing with escalating unbonded ratios. The failure progression of both beam types can be categorized into three stages: elastic phase, crack propagation phase, and compressive failure phase. The process of crack advancement, the load–deflection profile, and the load–slip behavior of the beams manifest similarities, albeit subject to variations attributable to the concrete matrix, bottom longitudinal reinforcement ratio, and unbonded ratio. The Menetrey–Willam constitutive model effectively replicates the load–deflection and load–slip characteristics of both beam types. However, its simulation precision is influenced by the friction coefficient existing between the rebar and the concrete matrix. Notably, this friction coefficient undergoes alteration in consonance with the concrete failure process, thereby reflecting the gradual degradation of bonding performance between the rebar and the concrete matrix.

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.

Axial compressive behavior of GFRP tube-reinforced concrete-steel double skin tubular columns

Hybrid FRP-reinforced concrete-steel double-skin tubular columns (DSTCs) exhibit the benefits of high bearing capacity, sufficient ductility and excellent durability. However, there are fewer studies on reinforced DSTCs under axial compression compared to unreinforced DSTCs. Eleven circular cross-section columns were tested to study the compressive behavior of GFRP-reinforced concrete-DSTCs. The main parameters considered were the thicknesses of GFRP tubes, longitudinal reinforcement ratio, hollow ratio and concrete strength. The test results showed that reinforced DSTCs had higher bearing capacity and better ductility than traditional DSTCs, and their bearing capacity could be increased by 36%–48%. The bearing capacity and initial stiffness increased with the increase of longitudinal reinforcement ratio, thicknesses of GFRP tubes and concrete strength, while they decreased with the increase of hollow ratio. When the load was within the range of 55%Pu, the restriction of the GFRP tube to the concrete was not obvious. Furthermore, an analytical model was established to predict the full load-strain curves of reinforced DSTCs, which considered the restraining effect of stirrups and the bi-axial stress state of FRP tube. The established model was in good agreement with most of the test results.

Experimental and numerical investigations on seismic behavior of spiral stirrup-confined square concrete-filled steel tubular columns

To investigate the seismic behavior of spiral stirrup-confined square concrete-filled steel tubular (SS-CFST) columns, ten square CFST columns, including eight SS-CFST columns and two ordinary CFST columns were experimentally studied through the cyclic loading tests. The critical test variables included the axial load ratio, spiral pitch, and longitudinal reinforcement ratio. First, the seismic behavior of the SS-CFST columns was herein discussed and clarified based on the failure modes, hysteretic response, skeleton curves, load-bearing capacity, strength and stiffness degradation, ductility and energy dissipation. Then, a total of 53 full-scale finite element (FE) models were established for parameter analysis of SS-CFST columns. The experimental and numerical results showed that the expansion deformation, necking and fracture of spiral stirrup were not formed when the SS-CFST columns were damaged, but the confinement effect effectively reduced the concrete fragmentation, alleviated the buckling of steel tube and longitudinal rebar, and limited the expansion of internal cracks. In the range of n=0.20–0.50, the ductility of SS-CFST columns significantly decreased with an increase in the axial load ratio, despite the stable bearing capacity and good energy dissipation of the columns. Moreover, unlike SS-CFST columns with high axial load ratio, spiral stirrup can only slightly improve the load-bearing capacity of SS-CFST columns with small axial load ratio (nt≤0.35). Compared with ordinary CFST columns, the strength degradation, ductility, collapse resistance, and energy dissipation of SS-CFST columns were significantly improved except for lateral stiffness, and the ultimate drift ratio of all SS-CFST columns in the test was greater than 3.00%. Furthermore, for SS-CFST columns, increasing the longitudinal reinforcement ratio can improve the lateral load-bearing capacity and stiffness. Finally, the formulas established in this paper can be adopted to assess the lateral load-bearing capacity of SS-CFST columns.

Displacement-based seismic performance of RC bridge pier

To correctly manage the road infrastructure before and after an earthquake, it is necessary to estimate and even predict the seismic performance of the bridge. The quantification of the bridge's seismic performance response was present in terms of displacement and also based on previous research of reinforced concrete bridge pier models. The displacement did define from a force lateral-displacement response diagram corresponding to the capacity curve, calculated through a non-linear static pushover analysis of the reinforced concrete bridge pier model for each limit state, from intact state to collapse. Thus, six defined displacements correspond to the cracking displacement, the yielding displacement, the spalling displacement, the crushing displacement, the buckling displacement, and the fracturing displacement. The six defined limit states correspond to the cracking limit state, the yielding limit state, the spalling limit state, the crushing limit state, the buckling limit state, and the fracturing limit state. Also, parametric analysis did carry out to evaluate the influence, relative importance, and trend of the input parameters in response to the seismic performance of the reinforced concrete bridge pier model. Eleven input parameters did analyze as the concrete compressive strength, the yield stress of reinforcing steel, the concrete cover thickness, the pier aspect ratio, the configuration of the transverse reinforcement, the spacing of the transverse reinforcing steel, the transversal diameter of the transverse reinforcing steel, the longitudinal reinforcement ratio, the transversal diameter of the longitudinal reinforcing steel, the axial load ratio, and coefficient of subgrade reaction.

Design approach and its optimization for bolted steel plate strengthened RC beams considering the effect of connection bolt slip

The use of bolted steel plates (BSP) has been found to be an effective method for increasing the flexural capacity of reinforced concrete (RC) beams. However, slip in bolt connections is an inevitable occurrence that affects the mechanical behavior of the BSP beam. While prior studies have thoroughly examined the effects of bolt connection slip on the flexural capacity of BSP beams, assuming unlimited slip, experimental results revealed that bolt connection failure takes place when slip surpasses a specific threshold. The current design methodology does not accommodate this finding. To address this issue, a simplified design method for practical applications is proposed. Comprehensive parameter studies were conducted on the enhanced moment capacity ratio and maximum bolt slip, involving a total of 13,824 and 276,480 calculations, respectively. It is found that several parameters (e.g., the aspect ratio of RC beam, the tensile longitudinal reinforcement ratio, the height of steel plate) affect the two above-mentioned indexes. Equations were then developed to determine the enhanced moment capacity ratio and maximum slip. It is noteworthy that the recommended effective yield slip (0.55 mm) is obtained based on adhesive anchor, which should be checked when other types of anchors would be used. Relying on these equations, an optimized design approach for BSP beams is introduced that avoids complex iterative processes. The effectiveness of the optimized design methodology is substantiated through a practical example.

Flexural performance of precast circular reinforced concrete members with intermediate connection filled with ultra-high-performance-concrete

Precast Reinforced concrete (RC) columns with circular sections are increasingly being utilized in the construction of RC structures. This paper reports investigations into the flexural behavior of precast circular RC members with an intermediate connection filled with Ultra-High-Performance-Concrete (UHPC). Experimental program and results are described of twelve RC circular members tested under four-point loads up to collapse. Of the twelve columns, three of them are solid ones without intermediate connection, while nine of them are precast Normal Concrete (NC) panels connected with UHPC. The studied parameters are the existence of an intermediate connection (with and without connection), the ratio of longitudinal reinforcement (µ) ratio and the length of steel bars embedded in the UHPC connection (Le). Three concrete types are used including Normal Concrete (NC), Strain Hardening Cementitious Composite (SHCC), and UHPC. Test results show that increasing the reinforcement ratio and the embedded length of the steel bars increases the strength and energy absorption of members. Finite element models (FEMs) developed using ABAQUS are presented for capturing the responses of RC columns incorporating different concrete types. The good agreement between computer simulation and experimental results suggests that the FEMs can be utilized to undertake further parametric studies with confidence.

Seismic performance objectives and quantitative deformation limits for superimposed RC shear walls with embedded bracings

To achieve performance-based evaluations for superimposed RC shear walls with embedded bracings (SRCXSW), their seismic performance objectives and quantitative deformation limits are established in this research based on the presentation of the seismic fortification targets and the parametric analysis of deformation limits by OpenSees. Research results exhibit that the seismic fortification targets proposed in this paper can meet the criteria of “Three-level Seismic Fortification Objectives” as stipulated in Chinese regulations, while also accommodating the owner’s desired performance requirements. The deformation indexes of SRCXSW are notably insensitivity to the arrangement of embedded bracings, the volume stirrup ratio and the reinforcement ratio in boundary element, while can be substantially affected by the axial load ratio and aspect ratio. In contrast to the longitudinal reinforcement and stirrup ratio in hidden columns, the volumetric ratio of the embedded bracings exerts a much more pronounced influence on the deformability of SRCXSW. Subsequently, an appraisal of the suggested deformation limits for SRCXSW, in conjunction with those outlined in current assessment codes, is carried out. It is common to observe inadequate safety margins when utilizing the deformation limits for cast-in-place RC shear walls in Eurocode 8 and ASCE/SEI 41. Conversely, the deformation limits proposed in this paper for SRCXSW are robust and offer ample safety margins for practical engineering applications.

A Finite Element Approach to Evaluate and Predict the Shear Capacity of Steel Fiber-Reinforced Concrete Beams

Adding steel fibers to a concrete matrix enhances the shear capacity of reinforced concrete beams. A comprehensive understanding of this phenomenon is essential to evaluate engineering designs accurately. The shear capacity of Steel Fiber Reinforced Concrete (SFRC) beams is affected by many parameters, such as the ratio of the shear span to the effective depth of the SFRC beam, the compressive strength of concrete, the longitudinal reinforcement ratio, volume fraction, aspect ratio, and the type of fibers. Therefore, to cover the influence of these parameters on the shear capacity of SFRC beams, 91 beams from previous studies, divided into 10 groups, were considered in the current study. Two approaches have been used to predict the shear capacity of SFRC beams. The first approach used 7 predicting equations derived from previous studies and the second one used finite element analysis (ANSYS software) to simulate the 91 beams. Despite the many approaches to simulate the structure elements, there is no reliable approach able to simulate satisfactorily 91 SFRC beams as this study does. The log file of ANSYS software was used to simulate and calculate the shear strength capacity of the beams. The results show a reasonable agreement with the experimental tests. The extracted results were much closer and more realistic than those obtained by the predicting equations. Also, the χ factor (squared value of experimental shear capacity to the predicted shear capacity) of the ANSYS software results is 97%, while the closest proposed equation gives 91%.