دانلود رایگان مقاله انگلیسی رفتار هیدرولیکی تیرهای کوپلینگ بتن تقویت شده مرسوم در دیوار برشی هموار شده با بتن مسلح - اشپرینگر 2017

Abstract:

This paper presents the experimental results of four full-scale coupling beams in which only horizontal reinforcements are placed, without diagonal reinforcements, with the aim to develop reinforcement details for coupling beams used in connecting side walls in a wall-slab structural system. Each coupling beam specimen was designed according to the deep-beam design procedure that does not use diagonal reinforcements and that is found in current standards. Two cases for basic deep-beam design specimens were investigated wherein (1) U-type reinforcement was added to prevent sliding shear failure of the joints and (2) horizontal intermediate reinforcements were placed. The coupling beam specimens were fabricated with a shear span-to-depth ratio (aspect ratio) of 1.68 and were connected to walls only by horizontal reinforcements, i.e., without diagonal reinforcement. The experimental results indicate that the strength of the beams was about 1.5 times the designed strength of a strut-and-tie model, which suggests that the model is available for predicting the strength of coupling beams with conventional reinforcement layouts such as horizontal and transverse reinforcement bars. The deformation capacity of these conventionally reinforced concrete coupling beams ranged from 1.48 to 3.47% in accordance with the reinforcement layouts of the beams. Therefore, this study found that the performance of conventionally reinforced concrete coupling beams with an aspect ratio of 1.68 can be controlled through the implementation of reinforcement details that include U-type reinforcement and the anchorage of intermediate horizontal bars.

6. Conclusions

An experiment on four full-scale coupling beam specimens was conducted to investigate the hysteresis characteristics of the coupling beams with horizontal reinforcements instead of diagonal reinforcements for wall-slab structural system. The study used reinforcement details for the connection between the beam and the wall as variables, based on reinforcement details required by current standards, to investigate the behavioral characteristics of coupling beams whose shear span-to-depth ratio is less than 2.0 and where only conventional reinforcement layouts are placed, i.e., without diagonal reinforcements. The following conclusions were drawn based on the test results.

(1) Coupling beams whose shear span-to-depth ratio was 1.68 and which were connected to walls only by horizontal reinforcements, without diagonal reinforcement, showed strength that is about 1.5 times the design strength for a strut-and-tie model, thus indicating that proper design strength is possible using these construction details. Overall, the deformation capacity was about 2%, which indicates a certain amount of deformation capacity. A pinching phenomenon, however, that occurred after the load reversals indicated a low level of energy dissipation.

(2) Horizontal reinforcements that were anchored in the walls for the lateral confinement of the beam led to an increase in beam strength. Even in cases where part of the horizontal reinforcement was not anchored into the wall, the design strength and a certain degree of ductility capacity were provided, and plastic hinges could be induced completely in the wall-beam joints. However, the strength gradually decreased after reaching the maximum force, which suggests that if the wall and beams are connected only with upper and lower horizontal reinforcements, the overall behavior is dominated by the flexural behavior of the joints, and the stress from the wall may not be transferred properly to the coupling beam when the connection is weak.