• Journal of the Korea Concrete Institute
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• v.15 no.4
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• pp.625-633
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• 2003

For the construction of open-topped steel box girder bridges, prefabricated concrete slab could offer several advantages over cast-in-situ deck including good quality control, fast construction, and elimination of the formwork for concrete slab casting. However, precast decks without reinforcements at transverse joints between precast slabs should be designed to prevent the initiation of cracking at the joints, because the performance of the joint is especially crucial for the integrity of a structural system. Several prestressing methods are available to introduce proper compression at the joints, such as internal tendons, external tendons and support lowering after shear connection. In this paper, experimental results from a continuous composite bridge model with precast decks are presented. Internal tendons and external tendons were used to prevent cracking at the joints. Judging from the tests, precast decks in negative moment regions have the whole contribution to the flexural stiffness of composite section under service loads if appropriate prestressing is introduced. The validity of the calculation of a cracking load fur serviceability was presented by comparing an observed cracking load and the calculated value. Flexural behavior of the continuous composite beam with external prestressing before and after cracking was discussed by using the deflection and strain data.

• International Journal of Concrete Structures and Materials
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• v.9 no.4
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• pp.415-425
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• 2015

Reinforced concrete beams with insufficient shear reinforcement were strengthened using glass fiber reinforced polymer (GFRP) plates. In the study, the effect of the number of bolts on the load capacity, energy dissipation, and stiffness of reinforced concrete beams were investigated by using anchor bolt of different numbers. Three strengthened with GFRP specimens, one flexural reference specimen designed in accordance to Regulation on Buildings Constructed in Disaster Areas rules, and one shear reinforcement insufficient reference specimen was tested. Anchorage was made on the surfaces of the beams in strengthened specimens using 2, 3 and 4 bolts respectively. All beams were tested under monotonic loads. Results obtained from the tests of strengthened concrete beams were compared with the result of good flexural reference specimen. The beam in which 4 bolts were used in adhering GFRP plates on beam surfaces carried approximately equal loads with the beam named as a flexural reference. The amount of energy dissipated by strengthened DE5 specimen was 96 % of the amount of energy dissipated by DE1 reference specimen. Strengthened DE5 specimen initial stiffness equal to DE1 reference specimen initial stiffness, but strengthened DE5 specimen yield stiffness about 4 % lower than DE1 reference specimen yield stiffness. Also, DE5 specimen exhibited ductile behavior and was fractured due to bending fracture. Upon the increase of the number of anchorages used in a strengthening collapsing manner of test specimens changed and load capacity and ductility thereof increased.

• Steel and Composite Structures
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• v.28 no.6
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• pp.709-718
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• 2018

Masonry walls are sometimes removed in buildings to either make new passages or increase the usable space. This may change the loading paths in the structure, and require new beams to transfer the loads which are carried by the masonry walls that are to be removed. One possible method of creating such new beams is to attach steel plates onto part of the existing walls to form a steel plate-masonry composite (SPMC) beam, leading to a new structure with part of the masonry wall supported by a new SPMC beam. This paper presents an experimental investigation into the interaction between the SPMC beam and the masonry wall above. Five SPMC beams supporting a masonry wall were tested to study the influence of parameters including the height-to-span ratio of the masonry wall, height of the beam and thickness of the steel plates. The test results, including failure mode, load-carrying capacity, load-deflection curves and strain distribution, are presented and discussed. It is found that for developing better arching effect in the masonry wall the ratio of the in-plane flexural stiffness of the masonry wall to the flexural stiffness of the SPMC beam must be between 2.8 and 7.1.

• Magazine of the Korea Concrete Institute
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• v.6 no.3
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• pp.152-161
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• 1994

Most widened bridges have been constructed by the joining-construction method that makes new and existing bridges structurally a single structure. Since the joining-construction method has several problems in design and construction viewpoint, this study is conducted in order to investigate the structural behaviors of RC slabs, which are widened and influenced by traffic-induced vibration of existing bridge during placing and curing of new concrete, with the prototype flexural strength test and FEM analysis. It was found that cracks are generated in construction joint at low applied load and that stress concentration at the joints and slips between steel bar and concrete are occured. But, the decreasing of load carrying capacity is negligible according to the traffic-induced vibration as well as the difference of construction method.

• Steel and Composite Structures
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• v.18 no.5
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• pp.1129-1144
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• 2015

Based on the experiment, this paper focuses on studying flexural behavior of splicing concrete-filled glass fiber reinforced polymer (GFRP) tubular composite members connected with steel bars. The test results indicated the confinement effects of GFRP tubes on the concrete core in compression zone began to produce, when the load reached about $50%P_u$ ($P_u$-ultimate load), but the confinement effects in tensile zone was unobvious. In addition, the failure modes of composite members were influenced by the steel ratio of the joint. For splicing unreinforced composite members, the steel ratio more than 1.96% could satisfy the splicing requirements and the steel ratio 2.94% was ideal comparatively. For splicing reinforced specimen, the bearing capacity of specimen with 3.92% steel ratio was higher 21.4% than specimen with 2.94% steel ratio and the latter was higher 21.2% than the contrast non-splicing specimen, which indicated that the steel ratio more than 2.94% could satisfy the splicing requirements and both splicing ways used in the experiment were feasible. So, the optimal steel ratio 2.94% was suggested economically. The experimental results also indicated that the carrying capacity and ductility of splicing concrete-filled GFRP tubular composite members could be improved by setting internal longitudinal rebars.

• Proceedings of the KSR Conference
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• 2002.05a
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• pp.183-188
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• 2002

In locations where the cost or concrete is relatively high, or in situations where the weight or concrete members is to be kept to a minimum, it may be economical to use hollow reinforced concrete vertical members. Hollow reinforced concrete columns with low axial load, moderate longitudinal steel percentage, and a reasonably thick wall were found to perform in a ductile manner at the flexural strength, similar to solid columns. However, hollow reinforced concrete columns with high axial load, high longitudinal steel percentage, and a thin wall were found to behave in a brittle manner at the flexural strength, since the neutral axis is forced to occur away from the inside face of the tube towards the section centroid and, as a result, crushing of concrete occurs near the unconfined inside face of the section. If, however, a steel tube is placed near the inside face of a circular hollow column, the column can be expected not to fail in a brittle manner by disintegration of the concrete in the compression zone. Design recommendation and example by moment-curvature analysis program for curvature ductility are presented. Theoretical moment-curvature analysis for reinforced concrete columns, indicating the available flexural strength and ductility, can be conducted providing the stress-strain relation for the concrete and steel are known. In this paper, a unified stress-stain model for confined concrete by Mander is developed for members with circular sections.

• Steel and Composite Structures
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• v.20 no.3
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• pp.487-500
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• 2016

In order to investigate the flexural bearing capacity of panel zone of diaphragm-through joint between concrete filled square steel tubular column and steel beam, four specimens were tested under static tension loads to study the mechanical properties and bearing capacity of diaphragm-through joints with a failure mode of panel zone. Finite element models of these specimens were developed to simulate the test and compare the predicted failure modes, load-displacement curves and bearing capacities with the experimentally observed. It was found that the tensile load from the steel beam flange is mainly shared by the square steel tube and the diaphragm. The diaphragm plastic zone appears along the cross-section lines enclosed by the square steel tube and the influence of steel beam web on the plastic zone of the steel tube is significant and cannot be neglected. Computational models of yield lines on square steel tube and diaphragm are established based on the distribution pattern of the plastic zone, and an analytical method for the evaluation of the bearing capacity of the joint is proposed. The theoretical results and the experimental data are compared and found in good agreement.

• Advances in materials Research
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• v.5 no.2
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• pp.121-130
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• 2016

In an attempt to reach a balance of performances in homo-polypropylene based system, the effects of single and hybrid reinforcements inclusions comprising calcium carbonate nanoparticles (2, 4 and 6 phc) and glass fibers (10 wt.%) on the mechanical and thermal properties were investigated. Different samples were prepared by employing twin-screw extruder and injection molding machine. In morphological studies, the uniform distribution of glass fibers in PP matrix, relative adhesion between glass fibers and polymer, and existence of nanoparticles in polymer matrix were observed. $PP/CaCO_3$ (6 phc) as compared to pure PP and PP/GF had superior tensile and flexural strengths, impact resistance and deformation temperature under load (DTUL). $PP/GF/CaCO_3$ (6 phc) composite displayed comparable tensile and flexural strengths and impact resistance to neat PP, while its tensile and flexural moduli and deformation temperature under load (DTUL) were 436%, 99% and $26^{\circ}C$greater respectively. The maximum impact resistance was observed in $PP/CaCO_3$(6 phc). The highest DTUL was perceived in PP hybrid nanocomposite containing 10 wt.% glass fiber and 4 phc $CaCO_3$ nanoparticle.

• Structural Engineering and Mechanics
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• v.84 no.2
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• pp.225-238
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• 2022

In order to improve the cracking resistance of reinforced concrete and give full play to the advantages of prefabricated assembly structure in construction, prestressed reinforced concrete composite beam (PRCC) is proposed. Through the bending static test of seven I-shaped beam specimens, the bending failure modes and bearing capacity of PRCC and reinforced concrete composite beam are compared and analyzed, and the effects of prestress size, prestressed reinforcement layout and prestress application sequence on the flexural behavior of PRCC beams are studied. The results show that the cracking load and ultimate load of PRCC beams significantly increased after prestressing, and prestressed tendons can effectively control the crack development. With the increase of prestressing degree, the deformation resistance and bending stiffness of PRCC beams are increased. The application sequence of prestress has little influence on the mechanical properties of PRCC beams. The crack width, stiffness and normal section bearing capacity of PRCC beam are analyzed, and the calculated results are in good agreement with the experimental results.

• Structural Engineering and Mechanics
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• v.14 no.2
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• pp.171-190
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• 2002

Two cases of design are performed for the hyperbolic paraboloid saddle shell (Lin-Scordelis saddle shell) and the hyperbolic cooling tower (Grand Gulf cooling tower) to check the design strength against a consistent design load, therefore to verify the adequacy of the design algorithm. An iterative numerical computational algorithm is developed for combined membrane and flexural forces, which is based on equilibrium consideration for the limit state of reinforcement and cracked concrete. The design algorithm is implemented in a finite element analysis computer program developed by Mahmoud and Gupta. The amount of reinforcement is then determined at the center of each element by an elastic finite element analysis with the design ultimate load. Based on ultimate nonlinear analyses performed with designed saddle shell, the analytically calculated ultimate load exceeded the design ultimate load from 7% to 34% for analyses with various magnitude of tension stiffening. For the cooling tower problem the calculated ultimate load exceeded the design ultimate load from 26% to 63% with similar types of analyses. Since the effective tension stiffening would vary over the life of the shells due to environmental factors, a degree of uncertainty seems inevitable in calculating the actual failure load by means of numerical analysis. Even though the ultimate loads are strongly dependent on the tensile properties of concrete, the calculated ultimate loads are higher than the design ultimate loads for both design cases. For the cases designed, the design algorithm gives a lower bound on the design ultimate load with respect to the lower bound theorem. This shows the adequacy of the design algorithm developed, at least for the shells studied. The presented design algorithm for the combined membrane and flexural forces can be evolved as a general design method for reinforced concrete plates and shells through further studies involving the performance of multiple designs and the analyses of differing shell configurations.