Influence Of Longitudinal Reinforcement Ratio Research Articles

Structural behavior of concrete slabs made of seawater sea sand and reinforced with GFRP reinforcement under flexural loading

Seawater sea sand concrete (SSC) structures reinforced with glass fibre-reinforced polymer (GFRP) reinforcing bars offer a promising alternative to conventional reinforced concrete, especially in the face of depleting clean water and river sand. However, comprehensive studies on the flexural performance and cracking behaviour of SSC structures reinforced with GFRP reinforcing bars are currently limited. This study delves into the influence of longitudinal reinforcement ratio on the flexural and cracking behaviour of SSC slabs reinforced with GFRP reinforcing bars under quasi-static loads, as well as the bond behaviour of GFRP reinforcing bar and SSC. The experimental program included 9 large-scale slabs and 30 pull-out specimens, revealing that the longitudinal reinforcement ratio significantly affects the flexural performance, particularly at higher load levels. Increased reinforcement ratio improved flexural stiffness, reduced deflection and crack width, enhancing load-carrying capacity and energy absorption. Although bond strength decreased at the serviceability load (up to 47%), a marginal reduction was observed at the ultimate state. The study proposes a semi-empirical equation for the effective moment of inertia of SSC slabs, accounting for the influence of reinforcement ratio on cracking moment and reduced bond strength of GFRP reinforcing bars. This equation aligns well with experimental results, demonstrating low error and coefficient of variation.

Shaking table test study on seismic performance of UHPC rectangular hollow bridge pier

To study the seismic failure mode and dynamic response characteristics of ultra-high performance concrete (UHPC) rectangular hollow bridge pier under dynamic loads, the El Centro wave, Taft wave, and Northridge wave were selected as seismic excitation for the shaking table test. The responses such as natural frequency, damping ratio, acceleration-time and displacement–time curves were investigated and the results were compared with the finite element simulation results. At the same time, 8 finite element models (FEMs) of UHPC rectangular hollow bridge pier were established to explore the influence of longitudinal reinforcement ratio and stirrup ratio on the seismic performance of bridge piers. The results indicated that with the increase of peak ground acceleration (PGA), the damping ratio, acceleration, displacement and UHPC strain of the specimen increased, while the natural frequency and the dynamic amplification factor of the pier decreased gradually due to the accumulation of damage. The increase of longitudinal reinforcement ratio improves the ductility, and the increase of stirrup ratio enhances the constraint effect of core UHPC and ductility to a great extent, which leads to different acceleration, displacement and equivalent plastic strain response of bridge piers. On the whole, the stiffness of UHPC rectangular hollow bridge pier was degraded after the input of seismic wave, but the ultimate bearing capacity was not deteriorated. The overall seismic performance is superior. In areas with low seismic fortification intensity, the reinforcement ratio of UHPC rectangular hollow bridge piers can be appropriately reduced.

NUMERICAL ANALYSIS ON MECHANICAL BEHAVIORS OF ASSEMBLED MONOLITHIC CONCRETE SHEAR WALLS WITH MORTISE-TENON JOINTS AND LOW SHEAR SPAN RATIO

A numerical analysis model of shear walls with mortise-tenon joints was established on the platform of finite element software ABAQUS. The influence of longitudinal reinforcement ratio of boundary element on mechanical behaviors of shear walls with mortise-tenon joints and low shear span ratio was studied. The results show that friction model can be used to simulate the new and old concrete interfaces of mortise-tenon joints. The calculation results of numerical analysis model are in good agreement with the test results, which can reflect the failure characteristics of shear walls with mortise-tenon joints. The bearing capacity of shear wall can be improved by increasing the longitudinal reinforcement ratio of boundary element, and the increase is more obvious when the reinforcement ratio is low. Vertical cracks occur along the lateral convex roots of shear walls with mortise-tenon joints, showing good deformation capacity. When the longitudinal reinforcement ratio of boundary element increases to 4.62%, brittle shear failure does not occur to the wall. When the horizontal reinforcement is 8@200, the longitudinal reinforcement ratio of boundary element exceeds 2.36%, the longitudinal reinforcement does not yield under the peak load, and flexural failure no longer occurs to the wall.

Seismic performance of precast short-leg shear wall using a grouting sleeve connection

Precast shear wall structures have been widely used in recent years due to their advantages of energy saving, environmental protection and efficient construction etc. The validity and reliability of connection methods are the key to ensure the performance of structures. In order to study the seismic behavior of precast short-leg shear wall connected with the grouting sleeve, a cast-in-place shear wall (OSSW) and a precast short-leg shear wall (PSSW) were designed and produced in this paper, respectively. The seismic indexes were obtained by low-cyclic reversed loading, such as failure mode, hysteretic behavior, stiffness degradation and energy dissipation capacity etc. The test results indicate that the failure of the specimens are controlled by bending instead of shear, but there is a noticeable difference in the cracking distribution between the two types of specimens. The bearing capacity of each feature point of PSSW is close to that of OSSW and the ductility and energy dissipation capacity of PSSW are slightly lower than that of OSSW. The data of test also reveal that the reinforcement bars connected by grouting sleeves are reliable before yielding, but the bonding strength between grouting material and the connecting reinforcement bar in the sleeve decrease after yielding. In addition, the finite element numerical simulation of PSSW is carried out to study the influence of longitudinal reinforcement ratio on the seismic indexes. With the increase of longitudinal reinforcement ratio, the bearing capacity and energy dissipation performance of PSSW are gradually enhanced. but the ductility of the specimen is reduced.

An experimental investigation on the shear and flexural behavior of steel reinforced HPSCC beams

High-Performance Self-Compacting Concrete (HPSCC) has experienced increasing demand over the past few years due to its enhanced mechanical properties and high bonding strength. These attributes make it preferable for use in structures, such as tall multi-story buildings, where high workability, strength and bending capacity are required. The objective of the present study is to investigate the shear and flexural behavior of HPSCC beams with no coarse aggregate and compressive strength of above 100 MPa. The influence of different types of steel fibre on the mechanical properties and failure modes of reinforced HPSCC beams were studied. In addition, the influence of the beam's span to effective depth ratio (a/d), longitudinal and transverse reinforcement ratios on the behavior of the HPSCC beams was studied. The results showed that the influence of the type of steel fibre is more significant than the influence of longitudinal reinforcement ratio. Moreover, the ultimate load and deformation capacity of HPSCC beams increased considerably for the beam specimens with steel fibre. However, it was shown that the non-fibre beams with d/4 shear link spacing had a higher ductility compared to the counterpart steel fibre beams with d/2 shear link spacing and with the same amount of longitudinal reinforcement ratio.

Behavior of ECC-encased CFST columns under axial compression

This paper presents an experimental study on the mechanical behaviors of engineered cementitious composite (ECC)-encased concrete filled steel tube (CFST) columns under axial loading. Six specimens, including four ECC-encased CFST columns and two concrete-encased CFST columns were tested. According to the test results, ECC-encased CFST columns showed both higher loading carrying capacity and more ductile behavior. The influence of longitudinal reinforcement ratio, stirrup ratio and the thickness of steel tube were discussed in this paper. Furthermore, a new method to calculate the carrying capacity of ECC-encased CFST columns was proposed and verified with experimental results.

Investigation on the Influence of Type of Steel Fibers on Shear Failure of HPFRCC Beams

This paper investigates the influence of different types of steel fiber on the mechanical properties of High Performance Fiber Reinforced Cementitious Composite (HPFRCC) as well as the shear failure mode of steel reinforced HPFRCC beams. Moreover, the influence of parameters such as span to effective depths (a/d) ratio of beams and longitudinal reinforcement ratio on shear strength of HPFRCC beams are examined. In reference to the results, despite the same tensile strength of both straight and hooked fibers utilized, the performance of straight steel fiber is superior to the hooked steel fiber due to its physiognomies. However, the beam specimens with straight steel fiber exhibit considerably lower deflection and ultimate load capacity when subjected to shear load. Also, the results show that the influence of type of steel fiber is more significant than the influence of longitudinal reinforcement ratio, i.e. the beam specimen with hooked steel fiber and 0.94% reinforcement ratio displayed higher deflection and ultimate shear load capacity compared to the specimen with straight steel fiber and 1.88% longitudinal reinforcement ratio.

Strength and behavior in shear of reinforced concrete deep beams under dynamic loading conditions

Research on reinforced concrete (RC) deep beams has seen considerable headway over the past three decades; however, information on the dynamic shear strength and behavior of RC deep beams under varying rates of loads remains limited. This paper describes the experimental results of 24 RC deep beams with and without shear reinforcements under varying rates of concentrated loading. Results obtained serve as useful data on shear resistance, failure patterns and strain rates corresponding to varying loading rates. An analytical truss model approach proves its efficacy in predicting the dynamic shear resistance under varying loading rates. Furthermore, three-dimensional nonlinear finite element (FE) model is described and the simulation results are verified with the experimental results. A parametric study is then conducted to investigate the influence of longitudinal reinforcement ratio, transverse reinforcement ratio and shear span to effective depth ratio on shear behavior. Subsequently, two empirical equations were proposed by integrating the various parameters to assess the dynamic increase factor (DIF) of maximum resistance under varying rates of concentrated loading.

Išilginio Armavimo Poveikis Gelžbetoninės Plokštės Praspaudžiamajai Laikomajai Galiai

This work presents the results of experimental tests on reinforced concrete slabs with different longitudinal reinforcement ratio ρ under concentrated load. Five series of specimen were made and tested, a total of ten slabs. The measurements of the specimens were 2135×2135×140 mm (Fig. 3). Longitudinal reinforcement ratio ρ = 0,449–1,90 %, the diameter of reinforcing bars was 8–16 mm, reinforcement bore yield stresses, spacing between bars was 100 mm. The protective concrete layer of the longitudinal reinforcement in all slabs was 20 mm. The cubic compressive strength of concrete fc,cube = 33,4–46,6 MPa. In the course of the experiment the measurements of the collapsing punching force, the radial and tangential deformations of the compression zone were made, the curves of their expansion were given, displacements of the column head were measured. The surface of the punching cone, irrespective of the longitudinal reinforcement ratio ρ, makes a ˜35° angle with the bottom (compression zone) surface of the slab. Deformations of radial and tangential directions in the compression zone during the course of cracking of the slab do not reach the ultimate compressive strains of concrete (3,50 ‰), the mean value of deformations in the radial direction is 1,6 ‰, the mean value of deformations in the tangential direction is 1,8 ‰, which allows to make a conclusion that the slab is punched-through under transverse collapsing force. The strength criterion of biaxial stress state proposed by Zalesov et al. (1973) and the expression of the resultant transverse force of the dowel action of the longitudinal reinforcement ratio ρ as proposed by Theodorakopoulos et al. (2002), were used to get the expression of the collapsing transverse force Vu which is given in equation (2). The factor of the influence of longitudinal reinforcement ratio ρ expressed through the resultant transverse force Vd of the dowel action makes 40–50 % of the collapsing force, Vd increases with increasing of the longitudinal reinforcement ratio ρ. The resultant transverse force Vc of the compression zone of concrete in the critical section makes 50–60 % of the collapsing force, Vc increases with increasing of the longitudinal reinforcement ratio ρ.

LOAD-DEFLECTION CHARACTERISTICS OF REINFORCED CONCRETE COLUMNS UNDER STATIC ALTERNATING CYCLIC LOADS

The objects of the study were columns of reinforced concrete viaducts used in large numbers for railway and urban transportation structures. The influences of variable factors such as longitudinal reinforcement ratio, hoop ratio, and axial load on behaviors of members such as limit states of crack occurrence, yielding and ultimate state of member, ductility, and load-deflection characteristics under static alternating cyclic loads were experimentally investigated.As a result, it was concluded that the load-deflection loop can be modelled as a maximum-point-directed type without slipping, that among various variable factors the influence of longitudinal reinforcement ratio is extremely great, and that plastic hinge length and longitudinal crack formation are determined by the combination of the quantities of longitudinal reinforcement and hoop reinforcement.