Ordinary Concrete Beams Research Articles

Shear behavior of reinforced glazed hollow bead insulation concrete beams

The application of glazed hollow bead insulation concrete can improve the seismic performance of the structure, simultaneously ensuring characteristics such as structural durability, fire resistance, thermal insulation, antifreezing, and impermeability. However, with change in material’s physical and mechanical properties, the shear resistance of vitrified microbead thermal insulation concrete members should be paid attention to. The literature search reveals only a few studies on the shear resistance of glazed hollow bead insulation concrete members. In this study, 14 glazed hollow bead insulation concrete beams and four ordinary concrete beams with C35 strength grade were tested. The mechanical failure process, failure form, failure mechanism, and the difference between vitrified microbead insulated concrete beam and ordinary concrete beam were compared. The effects of shear span ratio, hoop ratio and reinforcement ratio on the cracking load, ultimate load and failure mode were investigated. Combined with the “truss-arch” model, the shear bearing capacity of steel bar and concrete is described, and after considering the softening coefficient of glass microbead insulation concrete, based on the “truss-arch” model, a formula for calculating the shear capacity of inclined section of vitrified microbead insulated concrete beam was obtained. The results show that the shear failure test results of glazed hollow bead insulation concrete beams are similar to those of ordinary concrete beams; the shear bearing capacity of vitrified microbeads thermal insulation concrete beams is ∼13% higher than that of ordinary concrete beams under the same conditions, and stiffness degradation is slow in the later stage. After the constitutive relation and softening coefficient are modified, the “truss-arch” calculation model can be used to calculate the shear capacity of vitrified microbead insulated concrete beams, and the results are in good agreement with the experimental results. The study of the shear behavior of glazed hollow bead insulation concrete beams can provide data and technical basis for engineering application and has important theoretical significance and practical value to further understand the characteristics of this type of concrete structure, guiding engineering design, and promoting engineering application.

Research on Durability of Big Recycled Aggregate Self-Compacting Concrete Beam

Deflection and crack width are the most important durability indexes, which play a pivotal role in the popularization and application of the Big Recycled Aggregate Self-Compacting Concrete technology. In this research, comparative study on the Big Recycled Aggregate Self-Compacting Concrete Beam and ordinary concrete beam were conducted by measuring the deflection and crack width index. The results show that both kind of concrete beams have almost equal mid-span deflection value and are slightly different in the maximum crack width. It indicates that the Big Recycled Aggregate Self-Compacting Concrete Beam will be a good substitute for ordinary concrete beam in some less critical structure projects.

Seismic behavior of steel-reinforced recycled concrete inner-beam–column connection under low cyclic loads

This article presents the results of low cyclic loading tests on steel-reinforced recycled concrete inner-beam–column connections, including four 1:2.5 scaled specimens with different replacement rates of recycled coarse aggregates. The main objective of this study is to evaluate the seismic behavior of steel-reinforced recycled concrete inner-beam–column connection based on the seismic tests of the four specimens under low cyclic loads with vertical axial force. The main design parameter of the beam–column connections in this research is the recycled coarse aggregate replacement percentage. The crack status, failure modes, hysteresis loops, skeleton curves, energy dissipation, capacity stiffness of degradation, and ductility of steel-reinforced recycled concrete inner-beam–column connections are presented and analyzed. The results indicate that the main failure pattern of the steel-reinforced recycled concrete inner-beam–column connection is the shearing diagonal compression in the beam–column connection zone. As the recycled aggregate replacement percentage increases, both the bearing capacity and ductility of the steel-reinforced recycled concrete beam–column connections decrease to some extent. However, the seismic behavior of the steel-reinforced recycled concrete inner-beam–column connection does not degrade significantly compared with the ordinary steel-reinforced concrete beam–column connection.

Experimental study on torsional behavior of FRC and ECC beams reinforced with GFRP bars

The influence of fibers on the torsional behavior of GFRP reinforced concrete beams was studied. The polypropylene fiber (PP) was incorporated into concrete to improve the mechanical properties of the beams. A total of eight GFRP bars reinforced concrete beams with different fiber contents were tested under pure torsional loading. The test results indicated that the PP fibers could inhibit the crack propagations effectively, the spacing and width of the cracks were decreased. Under the allowable crack width of 0.7mm, the torsional moment of the fiber reinforced concrete (FRC) beams and engineered cementitious composite (ECC) beams were 10% and 40% greater than ordinary concrete beams respectively. Besides, within the fiber contents of 1.5%, the utilization intensity of the stirrups were enhanced by the fibers, the more the fiber contents was, the greater the torsional strength and the toughness of the beams were improved. Finally, empirical formulas for both cracking and ultimate torsional moments of the beams were proposed, the predicted values had good agreements with the experimental results.

STRENGTH AND CRACKER RESISTANCE OF BENDING ELEMENTS FROM HIGH-STRENGTH CONCRETE

The results of experimental studies of durability and crack resistance of reinforced concrete beams from high-strength concrete are presented and compared with ordinary concrete beams.

Flexural Test of Fly Ash based Geopolimer Concrete Beams

Fly ash is a by-product from the coal industry, which is widely available in Indonesia. Fly ash contains quite high silicate and alumina. Silica and alumina reacts with alkaline solution to produce alumina silicate gel which binds the aggregate to produce geopolymer concrete. Geopolymer concrete is introduced as an environmental concrete with high compressive strength. The use of geopolymer concrete beams is a solution to reduce the effects of greenhouse gases. This research uses experimental designs. The data are obtained from the testing of 4 pieces of reinforced geopolymer concrete beams and reinforced ordinary concrete beams with a / d of 1.11 and 2.24. The results are obtained from the maximum load that can be accepted by the beam. The results of this study are: (1) Geopolymer concrete cylinder has 26.78% higher compressive strength than ordinary concrete cylinders (2) Ordinary concrete beams can withstand 34.8% load higher compared to the geopolymer concrete beam (3) Reinforced ordinary concrete beams experience bending shear collapse while reinforced geopolymer concrete beam experience pure bending collapse.

Process of cracking in reinforced concrete beams (simulation and experiment)

The paper presents the results of experimental and theoretical investigations of the mechanisms of crack formation in reinforced concrete beams subjected to quasi-static bending. The boundary-value problem has been formulated in the framework of brittle fracture mechanics and solved using the finite-element method. Numerical simulation of the vibrations of an uncracked beam and a beam with cracks of different size serves to determine the pattern of changes in the spectrum of eigenfrequencies observed during crack evolution. A series of sequential quasi-static 4-point bend tests leading to the formation of cracks in a reinforced concrete beam were performed. At each loading step, the beam was subjected to an impulse load to induce vibrations. Two stages of cracking were detected. During the first stage the nonconservative process of deformation begins to develope, but has not visible signs. The second stage is an active cracking, which is marked by a sharp change in eingenfrequencies. The boundary of a transition from one stage to another is well registered. The vibration behavior was examined for the ordinary concrete beams and the beams strengthened with a carbon-fiber polymer. The obtained results show that the vibrodiagnostic approach is an effective tool for monitoring crack formation and assessing the quality of measures aimed at strengthening concrete structures.

Shear Capacity Research on Transversely Reinforced Concrete Beams

Inner transverse prestressed bars were used to enhance the shear capacity of concrete beams in this paper, which can be used in transformer beams to reduce the sectional size. Two transversely prestressed one ordinary concrete beams were tested and calculated by finite element method, and the following conclusions can be drawn: (a)The shear capacity of transversely prestressed concrete beam increase rapidly with the increase of the prestressing force level, which means that prestressing force level has a great influence on the shear capacity of transversely prestressed concrete beam. (b) The transverse prestressing bars can efficiently enhance the anti-crack performance of the reinforced concrete beams.

Preparation and Application of a Self-Thermal and Insulation-Ribbed Floor

With the cementitious composite formwork without being removed, steel wire frame and formwork technology, a self-thermal and insulation-ribbed concrete floor is made. Through the tests of bend-bearing capacity of self-thermal and insulation-ribbed floor, the results show that the loads of the self-thermal and insulation-ribbed floor meet the limits on deflection requirements according to the design of concrete structures. Besides, the floor has a better thermal and soundproof function compare to the ordinary concrete beam and slab, and its comprehensive cost of construction is low.

Analytical model for shear strength of ordinary and prestressed concrete beams

An analytical method employing the strain-based shear strength model was developed to predict the shear strength of prestressed concrete beams. The proposed method assumes that the shear force acting in a concrete beam is resisted primarily by the compression zone of intact concrete in the cross section. The shear capacity of the compression zone is evaluated at the inclined failure surface using the material failure criteria for concrete, considering the interaction with the compressive normal stress. Because the compressive stress is developed by the flexural action of the beam and the prestress applied to the cross section, the shear capacity is defined as a function of the flexural deformation and the prestress applied to the cross section. Then, the shear strength of the beam is determined at the intersection of the shear capacity curve and the shear demand curve. The proposed model was applied to existing test specimens. The results show that it can be used for both ordinary concrete beams and prestressed concrete beams.

Experimental Research on Ceramsite Concrete Beams

Six specimens, including 4 ceramsite concrete beams(one of beams mixed into the polypropylene fiber ) and 2 normal concrete beams, were tested to investigate the flexural behavior. The test results show that cracking load of ceramsite concrete beams is slightly smaller than the ordinary concrete beam and cracking load of ceramsite concrete beams has significantly improved after mixing into the polypropylene fibers. The ultimate load of ceramsite concrete beams are no less than ordinary concrete beam,and fibers have not effects on the increase of ultimate load. Load-deflection curves were compared,and the results show that stiffness of ceramsite concrete beam is less than ordinary concrete beam. Ductility of ceramsite concrete beam is poorer than ordinary concrete beam. Fibers improve the stiffness of ceramsite concrete beam. Cover thickness of concrete beam has little effect on the performance of ceramsite concrete beam.

Experimental Study on Shear Behavior of Combined Aggregate Concrete Beams

Based on the test，the shear behavior of combined aggregate concrete beams is studied. The results show that combined aggregate concrete beam have similar behavior with ordinary concrete beams, and the shear capacity reduces with the increase of lightweight aggregate. And design formula of the combined aggregate concrete shear capacity is suggested.

Evaluation of the efficiency of UHP-SHCC beams in flexure under external prestressing (comparative study)

Externally prestressed beams are structural concrete members in which prestressing tendons are placed outside the concrete section. Design provisions of many international codes for external prestressed beams are limited to ordinary concrete (OC). However, the main advantage of using an ultra high performance strain hardening cementitious composite (UHP-SHCC) is to increase the flexural load-carrying capacity for concrete members. The aim of this research was, therefore, to find the coupling effect of external prestressing and the use of UHP-SHCC. To achieve this objective, three prototype beams were tested to evaluate the effect of prestressing on the behaviour of UHP-SHCC beams. The experimental results were also compared with those of an OC beam. Basic section analysis was carried out on uncracked, cracked elastic and ultimate strength conditions. The analytical model was verified and validated against experimental tests. An extensive parametric study using a basic analysis was carried out for prestressed UHP-SHCC beams under quasi-static monotonic loading. Comparative studies were conducted to achieve the efficiency of UHP-SHCC beams under external prestressing as compared with ordinary and high-strength concrete (HSC) beams with and without reinforcement. The test results indicate the efficiency of using UHP-SHCC material with external prestressing to improve the failure loads and ductility of beams relative to ordinary and HSC beams.

Experimental Study of Pre-Stressed Concrete Beams with Fatigue Subjoining Freezing-Thawing Circle

Based on fatigue tests of pre-stressed concrete (PC) and ordinary concrete beams for 15 specimens after different times of freezing-thawing circle, the degradation process for the tested beams of the relative dynamic elastic modulus is conducted. The experimental study shows that the pre-stressing level and times of freezing-thawing circles are main influence factors to durability of test beams. The results of this study are useful for the exploration of the mechanism of the PC structure’s damage and the improvement of design theory concerning the durability of the PC structures.

Experimental Study on Flexural Bearing Capacity of Reinforced Ceramsite Concrete Beam

In order to investigate the flexural bearing capacity of reinforced ceramic concrete beams, static loading experiments were carried out. 10 ceramic reinforced concrete beams and 2 non-reinforced ceramic concrete with different steel ratios, cover thicknesses and bar diameters were fabricated. The gauges of concrete was arraged on the surfaces of section in mid-span and and steel gauges was arraged on the surfaces of steel bars. The loading device was consisted of a 200kN hydraulic jack, a distributive girder and reaction frame while the dial indicators was arraged in supports and mid-span. The strain of concrete and steel bar in different loading along with the crack,yield and utimate of load were recorded .It found that the stress-strain law, crack extension regularity , failure modes of specimens was similar to the ordinary concrete beams and the current procedures formulas about flexural bearing capacity is reliability. It also found that both ceramic aggregate and cement mortar were crushed for the perfectly bonding of the interface and the strength of aggregate was to be fully utilized.

Research on Flexural Behavior of Coarse Recycled Aggregate-Filled Plain Concrete Beam

In order to study the flexural behavior of coarse recycled aggregate-filled plain concrete beams, two beams were made. The experiment of simply supported beam under concentrated loads is performed, which makes us get the ultimate flexural capacity, midspan deflection and the development of cracks of each beam, and the numerical simulation of the damage process of beams is also carried out using finite element software. The results indicated that the tension property of coarse recycled aggregate-filled plain concrete beam is better than ordinary concrete beam, and some failure forms of bending is similar; the strength of recycled aggregates greatly influences flexural behavior of coarse recycled aggregate-filled plain concrete beam.

Rehabilitation of Concrete Beam by Using Martensitic Shape Memory Alloy Strands

The rehabilitation properties of intelligent concrete beam reinforced with shape memory alloys (SMA) is investigated. In this study, SMA strands, made of 7 single wires, are used to replace the steel bars in ordinary concrete beam. The test of single point loading at the mid-span is conducted on the beam. The experiment has three stages including loading, unloading and heating the SMA strands. During heating the SMA strands by electrical current, the crack width can be reduced by taking the advantage of the shape memory effect of SMA strands. The results illustrate that SMA is a candidate material for rehabilitation of reinforced concrete structures.

Experiment on Bending Performance of Double Mixing HPC Concrete Beam under the Artificial Climate Environment

Through the experiment on HPC beam which is subject to artificial climate conditions and indoor natural environment, section strain, beam load-deflection curve, failure and cracks are studied. The results show: compared with ordinary concrete beam, the HPC beam which has been subject to artificial climate conditions has higher stiffness; the deflection amount and the width of crack of this concrete beam all fall in the confines of ultimate service state under use load; and the beam displays a better ductility in failure

Research on Flexural Behaviors of Cementitious Composite Material Formwork without Being Removed Concrete Beams

Based on experiments on two beam specimens (one is a concrete beam with a formwork without demoulding, another is a normal concrete beam), the basic mechanical properties of the flexural beam with a formwork without demoulding, in the condition of monotonic loads were studied, including failure patterns, normal section bearing capacities, change rules of deflections, concrete strain of midspan, strain of strengthened reinforcing steer and so on. The comparison of bearing capacity is also made between a concrete beam with a formwork without demoulding and an ordinary concrete beam. The results indicate that by calculating bend-bearing capacity in current code, a beam with a formwork without demoulding is as safe as an ordinary concrete beam, a concrete beam with a formwork without demoulding meets the requirements of deflection limit value. Its bend-bearing capacity is approximate to an ordinary concrete beam.

A comparative study of LECA concrete sandwich beams with and without core reinforcement

Lightweight concrete beams of sandwich construction with and without core reinforcement were made using Lightweight Expanded Clay Aggregate (LECA) concrete cores, and tested in four-point loading. The programme included tests on ordinary dense concrete beams which had the same reinforcement, and were used as controls. Results of beam deflections, strains and ultimate loads were recorded. The comparative study illustrated that sandwich beams cored by LECA concrete, with the cores reinforced, had sufficiently good shear resistance for the beams to fail by yielding of the tension steel, and that if strength-to-weight ratio is taken as a measure of efficiency, the sandwich beams were more efficient structures than the ordinary dense beams.