Reinforced Concrete Coupling Beams Research Articles

Experimental and numerical evaluation of seismic behavior of coupled walls connected by post-tensioned, unbonded, precast concrete coupling beams

To investigate the seismic performance of coupled shear walls, which are connected by post-tensioned, unbonded, precast concrete coupling beams (PCCB), two 1/7-scale experiments with 8-story coupled shear walls under cyclic lateral loadings were conducted. Coupling of concrete shear walls is achieved by post-tensioning concrete beams to the wall piers using unbonded post-tensioning tendons (UPT) at the floor and roof levels. Experimental results show that little damage occurs in the coupling beams and the wall regions when the specimen undergoes large nonlinear displacements. The residual displacements of the specimen are small because of the restoring effect of the post-tensioning force. The seismic performance of three systems including CW-RC (coupled wall systems that use traditional RC coupling beams), CW-UP (coupled wall systems which use only post-tensioning tendons without steel reinforcement through the beam-wall joints), and CW-HUP (shear walls and PCCB that use combinations of steel reinforcement and post-tensioning tendons) are evaluated by means of nonlinear dynamic analysis. The calculation results indicate that the inter-story drift and peak lateral displacements of CW-HUP and CW-UP are greater than that of CW-RC, whereas the residual deformations are reduced because of the self-centering effect of the post-tensioning tendons.

Post-Earthquake Strengthening of RC Coupling Beams with GFRP Wrapping: Experimental Investigation.

This research aims to address a post-earthquake urgent strengthening measure to enhance the residual seismic capacity of earthquake-damaged reinforced concrete wall structures with coupling beams. The study consists of a series of tests on half-scale prototype coupling beams with various detailing options, including confined with reduced confinement, partially confined, and unconfined bundles, under cyclic loading conditions. The methodology employed involved subjecting the specimens to displacement-controlled reversal tests, and carefully monitoring their response using strain gauges and potentiometers. The main results obtained reveal that GFRP wrapping significantly enhances the seismic performance of earthquake-damaged coupling beams, even in cases where specimens experienced strength loss and main reinforcement rupture. The strengthened beams exhibit commendable ductility, maintaining high levels of deformation capacity, and satisfying the requirements of relevant seismic design codes. The significance of the study lies in providing valuable insights into the behavior and performance of damaged coupling beams and assessing the effectiveness of GFRP wrapping as a rapid and practical post-earthquake strengthening technique. The findings can be particularly useful for developing urgent post-earthquake strengthening strategies for high-rise buildings with structural walls. The method may be particularly useful for mitigating potential further damage in aftershocks and eventual collapse. In conclusion, this study represents a significant advancement in understanding the post-earthquake behaviors of coupling beams and provides valuable guidance for practitioners in making informed decisions regarding post-earthquake strengthening projects. The findings contribute to the overall safety and resilience of structures in earthquake-prone regions.

Evaluation of performance and storey drift ratio limits of high-rise structural systems with separated gravity and lateral load resisting systems using time history analysis and incremental dynamic analysis

To increase the efficiency of prefabricated construction of high-rise structure, a composite structural system with separated gravity and lateral load resisting systems (referred to as a ‘new separable system’) is proposed. Efficient numerical models of the composite frames, reinforced-concrete (RC) shear walls, RC coupling beams, and braces in the new separable system were developed using the finite-element program MSC.Marc. The fragility curves of these components were developed through parametric analysis and a literature review of previous research and database documents. Through time history analysis, the responses of roof displacement, storey drift, and residual drift were analysed and compared with those of the traditional composite frame–shear wall system. An incremental dynamic analysis (IDA) was performed to obtain the IDA curves of the new separable system and the traditional system, and the seismic fragility curves of the two systems were built. The seismic performance of the new separable system was compared with that of the traditional system in terms of the collapse probability, dynamic safety factor, and risk of seismic damage. The results indicated that for high-rise composite structural systems with separated gravity and lateral resisting systems under frequently occurring earthquakes, the reasonable range of the storey drift ratio limit in design is 1/800 to 1/1000, and a limit value of 1/1000 is recommended conservatively.

Evaluation and story drift ratio limits of structures with separated gravity- and lateral-load-resisting systems using pushover analysis

In recent years, China has strongly advocated the development of prefabricated buildings. To meet the growing demand for housing construction, it is necessary to develop high-rise prefabricated structures. To increase the construction efficiency of high-rise prefabricated structures, an innovative composite structural system with separated gravity- and lateral-load-resisting systems (referred to as an ‘innovative structural system’) was developed, and its seismic performance was evaluated. At the component level, efficient numerical models of the composite frames, reinforced-concrete (RC) shear walls, RC coupling beams, and braces in the innovative structural system were developed using the general finite-element software MSC.Marc. The fragility curves of these components were developed through parametric analysis and a literature review of previous research and database documents. At the system level, through finite-element analysis, the seismic mechanism of the innovative structural system under lateral loads, including the lateral displacement pattern, plastic development pattern, and failure mode, was compared with that of the traditional composite frame–shear wall system. A static pushover analysis was performed, and the displacement response results of the innovative structural system under the maximum considered earthquake strength were obtained. The damage to the components was evaluated via fragility analysis, and the seismic performance of the innovative structural system was compared with that of the traditional system according to the safety factor. The results indicated that for high-rise composite structural systems with separated gravity- and lateral-load-resisting systems under frequently occurring earthquakes, the reasonable range of the story drift ratio limit in design is 1/800 to 1/1000, and a limit value of 1/1000 is recommended conservatively.

Strengthening of deep RC coupling beams with FRP composites: A numerical study

Currently, most buildings have earthquake-resistant systems such as coupled shear walls and couple beams, designed based on previous code specifications. Also, due to specifications of new codes, diagonal reinforcement details in coupled beams are introduced, which due to the high reinforcement congestion, creates problems in fabrication and pouring. The main goal of this paper is to numerically study retrofitting with polymer composites reinforced with carbon fiber with external bonding for reinforced concrete coupling beams. The previous studies are divided into three categories. The first part concerns using externally bonded composite FRPs and the effect of fiber arrangement and thickness on the coupled beam behavior. The maximum displacement ductility in shear reinforcement patterns belonged to I and 2I patterns, which had the maximum ductility coefficients of 7.04 and 8.87. By comparing 7 CFRP reinforcement patterns, results showed that due to the mixed failure mode (flexural-shear) of the coupling beam, the U-X reinforcement pattern increased the load-bearing capacity by 18% compared with the base sample. By using suitable anchorage and preventing premature debonding, this method could be introduced as an effective method for improving the coupling beam’s behavior. In the second category, reinforcement with composite FRPs was compared with diagonal reinforcement and strengthening by installing steel plates and the accompanying behavior diagrams were given. Compared with other reinforcement methods in terms of load-bearing capacity and ductility, the specimen reinforced with CFRP and steel plates had a 49% and 70.4% increased load-bearing capacity of the control specimen. Among the studied specimens, the best performance belonged to the specimen with diagonal reinforcements, which had an increased load-bearing capacity and ductility of 124% and 4.2% compared with the base specimen. Finally, the third part is about the effective parameters of the coupling beam such as span length to height ratio and longitudinal reinforcement value regarding coupling beam behavior.

One-sided shear retrofit of reinforced concrete beams in existing high-rise buildings

This paper presents the evaluation of one-sided shear retrofit schemes for reinforced concrete (RC) coupling beams in existing buildings. Three full-scale beam Specimens CB1, CB2 and CB3 are planned for cyclic tests. Specimen CB1 represents a RC coupling beam in existing 24-story RC buildings, completed in Taiwan, 2017. Specimens CB2 and CB3 are retrofitted by added stirrups in the increased beam cross section and a bolted a steel plate from only one side of the RC beam, respectively. Test results showed that the shear strengths of the two retrofitted specimens exceeded the force of the RC coupling beam expected at the maximum considered earthquake (MCE) level. Specimen CB1 exhibited flexural-shear failure during the cycle of 5% drift. Specimens CB2 and CB3 exhibited shear failure during the cycle of 4% drift, and then concrete crushing associated with longitudinal bar buckling in the plastic hinge region. The peak shear forces of the added stirrups in Specimen CB2 and of the added steel plate in Specimen CB3 were 34 and 22% of the total shear forces, respectively, at large drifts. The added stirrups in the increased beam cross section provided larger shear force than the bolted steel plate. Both schemes were used to retrofit RC beams in the existing high-rise buildings in New Taipei City.

Numerical study of reinforced concrete coupled shear walls based on a two-dimensional finite element model

The reinforced concrete (RC) coupled shear wall is used extensively in high-rise buildings due to its extraordinary lateral resistance performance. Although massive individual RC shear wall as well as RC coupling beam specimens were tested, both the experimental and numerical studies on the seismic performance of RC coupled shear walls are insufficient. Considering the difficulties in large-scale coupled shear wall tests, finite element analysis (FEA) is carried out in this study to reveal quantitatively the effects of coupling beams with different aspect ratios and reinforcement layouts, as well as the behavior of coupling beams in the complex boundary conditions between adjacent wall piers. First, the finite element model based on a two-dimensional fixed crack constitutive model is proposed and validated by twelve coupling beam tests and the results demonstrate that buckling of diagonal bars should be reasonably considered. Then three coupled shear wall specimens are simulated, verifying the high accuracy of the proposed model. The effects of slabs on the coupled shear wall as well as coupling beams are also discussed. Finally, twenty coupled shear wall models with different degrees of coupling (DOCs) and diagonal bar ratios of coupling beams are analyzed. The results demonstrate that coupled shear walls with the diagonal bar ratio of 25–75% exhibit equivalent seismic performance with the diagonal bar ratio of 100%. In order to make full use of the energy dissipation of coupling beams, the DOC value should be no larger than 66%. With the constraint of adjacent wall piers, large axial compressive and tensile forces are induced, and their effects on the coupling beams should be considered.

Development of novel self-centering steel coupling beams without beam elongation for earthquake resilience

Reinforced concrete (RC) coupled walls are extensively used as the seismic-resistant structural system of tall buildings in high seismic zones. In RC coupled wall systems, the coupling beams are typically designed and detailed to dissipate energy through large inelastic responses to meet the expected seismic performance under moderate-to-strong earthquakes. However, costly excessive repair or even complete demolition caused by the considerable damage in conventional RC coupling beams is usually inevitable. Such disadvantage of RC coupling beams has increased the interest on replaceable steel coupling beams, which can isolate the damage concentrated in the fuses; thus, these beams are expected to be replaced after a strong earthquake. However, replacing these beams in practice is difficult if considerable residual deformation exists in these replaceable fuses. Therefore, seismic resilience cannot be explicitly guaranteed. For this reason, this study proposes a novel self-centering (SC) steel coupling beam that incorporates superelastic shape memory alloy (SMA) bolts and steel angles. The SC steel coupling beam is composed of two elastic beam segments and one rocking segment. Elastic beam segments are designed by steel beams that connect to the RC walls at both ends of the coupling beam, whereas the rocking segment located in the middle of the coupling beam is controlled by the SMA bolts and steel angles. Two ingenious shear keys are designed between the elastic beam segments and the rocking segment; these shear keys help the SC coupling beam to exhibit centerline-rocking behavior that is free from beam elongation. The working principle of the novel SC steel coupling beam is described first. Then, the cyclic responses of the SMA bolt and the steel angle, which are the two core components in the SC steel coupling beam, are investigated. The seismic performance of the SC steel coupling beam is computationally investigated in consideration of the effects of steel angles and the prestrain in the SMA bolts. Results show that the proposed SC steel coupling beams exhibit excellent SC capability and energy dissipation. Most damage is isolated in the steel angles, which can be easily and rapidly inspected or replaced after earthquakes without operation interruption. Importantly, beam elongation is almost eliminated under cyclic loading. With these advantages, the SC steel coupling beam can provide a promising solution for high-performance coupled wall systems.

Effect of Axial Restraint and Loading History on the Behavior of Short Reinforced Concrete Coupling Beams

Effect of Axial Restraint and Loading History on the Behavior of Short Reinforced Concrete Coupling Beams

Investigation of Damage Limits of Conventional Reinforced Concrete Coupling Beams

Türkiye Bina Deprem Yönetmeliği 2018 (TBDY, 2018)’de geleneksel donatılmış betonarme bağ kirişleri için öngörülen şekil değiştirme esaslı hasar sınırları analitik olarak incelenmiştir. Geleneksel donatılmış betonarme bağ kirişlerinin çekme ve basınç donatısı oranı, enine donatı çapı ve aralığı sabit tutulmuş net açıklık / derinlik oranı ve beton basınç dayanımını değiştirilerek SAP 2000 programı ile moment-eğrilik değerleri hesaplanmıştır. Bu çalışmada; gerçek malzeme davranışları esas alınmıştır. Elde edilen momenti-eğrilik ilişkilerinden betonarme bağ kirişlerinin elastik ötesi davranışları incelenmiştir. Geleneksel donatılmış betonarme bağ kirişi modelleri için moment-eğrilik ilişkilerinden elde edilen veriler kullanılarak TBDY, (2018)’de verilen hasar sınır değerleri betonarme bağ kiriş modelleri için hesaplanmıştır. Şekil değiştirme değerleri TBDY (2018)’de tanımlanmış olan göçmenin önlenmesi (GÖ), kontrollü hasar (KH) ve sınırlı hasar (SH) performans seviyeleri için hesaplanmıştır. Geleneksel donatılmış betonarme bağ kirişleri için üç ayrı hasar sınırı ve bu hasar sınırlarına karşı gelen birim şekil değiştirme değerleri incelenmiştir. Geleneksel donatılmış betonarme bağ kirişlerde farklı performans düzeyi için beton ve donatı çeliği birim şekil değiştirmeleri ve plastik dönmeleri hesaplanarak performans düzeyleri araştırılmıştır. GÖ ve KH performans düzeyleri için plastik dönmelerin hasar sınırları; akma eğriliği, kopma eğriliği, plastik mafsal uzunluğu, kesme açıklığı ve boyuna donatı çapının fonksiyonu olarak tanımlanmıştır. Bu çalışmada; geleneksel donatılmış bağ kirişlerinin beton basınç dayanımının akma momentine (M_y), GÖ ve KH performans düzeyleri için plastik dönme sınırlarına (θ_P^((KH)) ve θ_P^((GÖ))) etkili olduğu gözlemlenmiştir. Net açıklık derinlik oranın (l_n/h) artırılması; geleneksel donatılmış betonarme bağ kirişlerininGÖ ve KH performans düzeyleri için izin verilen plastik dönme sınırlarına (θ_P^((KH)) ve θ_P^((GÖ))) ve akma durumu için yer değiştirmiş eksen dönmesi üzerine (θ_y) etkili olduğunu ispatlanmıştır.

Application of hybrid simulation method for seismic performance evaluation of RC coupling beams subjected to realistic boundary condition

SummaryIn a building subjected to seismic loading, large compressive force may develop in reinforced concrete (RC) coupling beams because of axial restraint imposed by the neighboring shear walls against the elongation of the coupling beams during the failure process. The axially compressive force can increase the shear stiffness and strength of the coupling beam and may change its failure mode. In this paper, a novel coupling beam testing procedure adopting hybrid simulation method is proposed in which the axial restraint is determined through hybrid simulation and the calculated axial restraint is imposed on a specimen during the test. RC coupling beams were tested by adopting both the proposed test procedure and the conventional testing approach in which the effect of the axial restraint is not accounted for. Test results depict a clear difference in the response of the coupling beam, such as shear capacity and failure mode, depending on the consideration of the axial restraint during the test. The test outcome demonstrates the usefulness and applicability of the proposed test procedure.

Effect of deviation angle between principal stress and diagonal reinforcement direction on seismic performance of RC coupling beams

In a coupled shear wall system, the reinforced concrete (RC) coupling beams are allowed to form plastic deformations in order to dissipate seismic energy while maintaining the stability of overall structural system. However, the coupling beams are generally shear-dominated members because of their short shear span-depth ratio, which is usually less than 2. Therefore, under high seismic shear demand, the energy dissipation capacity and ductility of these members are sharply reduced compared to RC beams with larger shear span-depth ratio due to severe pinching effect. In order to avoid any undesirable structural behavior, the current standards stipulate the use of diagonal reinforcing bars in RC coupling beams with short span-depth ratio. Previous studies show that the diagonal reinforcement arrangements improve the structural performance of coupling beams, but the behavior of such members under cyclic bending and shear may significantly vary depending on the orientation of diagonal reinforcement. In this study, the effects of deviation angle between principal stress and diagonal reinforcement direction in the failure region, were experimentally investigated considering the potential failure modes of the coupling beams. Six RC coupling beams were tested under reversed cyclic bending and shear during this research. Experimental results show that the ductility ratio and the energy dissipation capacity of RC coupling beams vary, depending on the orientation of the diagonal reinforcement even when the same amount of diagonal reinforcement is provided. The structural performance of RC coupling beams improves as the deviation angle between direction of principal stress and the diagonal reinforcement becomes smaller. Finally, a finite element method (FEM) analysis was carried out for the test specimens. The FEM analysis results closely agreed with experimental observations that both the ductility ratio and energy dissipation capacity were larger for members with lowest deviation angle.

Cyclic Experiments on Concrete-encased CFST wall-RC Coupling Beam Joints with Non-through-core Anchorages

ABSTRACT In this study, a new type of non-through-core anchorage is proposed to anchor longitudinal reinforcing bars (rebar) in reinforced concrete (RC) coupling beams into concrete-encased, concrete-filled, steel tube (CFST) composite shear walls. The cyclic behaviour and anchorage performance of the coupling beams is investigated. The concrete-encased CFST wall consists of two boundary CFST components and an outer RC component. U-shaped reinforcing bars are embedded in the concrete-encased CFST wall to anchor the longitudinal rebars into the RC coupling beams. Cyclic loading tests are conducted on six wall-beam joint specimens, for a constant axial load on the wall and a cyclic load on the coupling beam. The test parameters include the rebar anchorage construction, the concrete strength, and the span-depth ratio of the RC coupling beam. The test results are used to perform a detailed analysis of the failure modes, hysteretic responses, strains, skeleton curves, bearing capacities, ductilities, and energy dissipation capacity. The specimens exhibit highly stable hysteresis behaviour and large inelastic rotation with a high damage tolerance. Slippage is observed after the appearance of diagonal shear cracks, which lead to clear pinched hysteresis behaviour. Interestingly, the buckled longitudinal rebars develop strain later than the directly anchored longitudinal rebars. The proposed anchorage construction can accommodate the largest residual deformation and has a reliable anchoring capacity.

Seismic response assessment of a hybrid coupled wall structure with novel self-centering steel truss coupling beams

In this paper, a novel self-centering buckling-restrained energy dissipater (SC-BRED) with pretensioned basalt fiber-reinforced polymer composite tendons is firstly introduced. Furthermore, based on the SC-BREDs, a self-centering steel truss coupling beam (SCCB) is proposed to improve the seismic resilience of coupled wall structures. The SCCB consists of chord members at the top and bottom, respectively, and two SC-BREDs are employed in the diagonal direction. The chords are connected to the adjacent wall piers by hinge joint and all inelastic deformations are concentrated on the SC-BREDs, which can be easily installed and quickly repaired for post-earthquake. This paper mainly focused on the numerical and theoretical analyses of the SCCB, and nonlinear numerical models are developed in PERFORM-3D. An 11-story prototype structure was designed per Chinese code. The seismic behaviors of the hybrid coupled wall system with SCCBs (HCW-SC), the hybrid coupled wall system with steel truss coupling beams (without pretensioned tendons), and the reinforced concrete coupled wall system with RC coupling beams were evaluated and compared under maximum considered earthquake. Results showed that the HCW-SC can achieve excellent lateral strength, stiffness, and ductility as well as reduce the residual displacements of the structure after earthquake.

Seismic performance of double skin semi-base-isolated structures

Base isolation technology is a popular and powerful isolation technology. This technique can greatly reduce the seismic response of the structure, so as to reduce the damage to the structure. Base isolation method decouples the superstructure from the base by installing a flexible layer under each column to reduce dynamic response in the earthquake and elongate the time period of structures due to its inherent flexibility. However, the long time period causes large displacement. In addition, base isolation devices are highly vulnerable due to uplift forces produced by lateral force resisting systems (LFRS). In this study, an adjustable structure with a new configuration, namely double skin semi-base-isolated (SBI) structure is presented to solve the above problems. The LFRS is omitted in the proposed SBI structure and the time period and displacement are reduced compared to the conventional base-isolated structure. The forcedeformation behavior of an isolator is modeled as bi-linear hysteretic behavior which can be effectively used to model all isolation system in practice. This study investigates the seismic performance of 10-story double skin SBI reinforced concrete (RC) structure under far-fault earthquake ground motion by numerical method. Results demonstrate that the SBI system is significantly adjustable with the use of RC coupling beams between the inner core and outer frames. By increasing or reducing the number of connected floors in the SBI system, dynamic behaviors of the SBI system can be changed. The adjusted structure can be created by adding and removing RC coupling beams at every arbitrary floor level.

Invistigating the effects of frp bars on the seismic behavior of reinforced concrete coupling beams

Sometimes, it is necessary to install regular openings like windows or doors in the shear walls. Such openings require special reinforcement. There are several methods for reinforcing deep beams, one of which is the use of fiber reinforced polymer bars. In this study, an experimental work on a coupled shear wall has been used to mode the system by using finite element method with ABAQUS software. The finite element model was established based on part of the experimental study and verified with the other parts of the experimental results. The comparison shows good agreement. In the study, three different types of fiber reinforced polymer bars were considered in improving the mechanical and structural behavior of RC coupling beams. Results of the finite element analysis showed the superiority of the CFRP bars in improving seismic behavior of the coupled shear wall comparing to GFRP and BFRP.

Experimental Study on a Hybrid Coupling Beam With a Friction Damper Using Semi-steel Material

RC coupling beams have been reported serious damages during 2008 Wenchuan earthquake. Once cracks occurred, it is very difficult to repair. To improve the ductility and reparability of the traditional RC coupling beam, a damage-controllable hybrid coupling beam is proposed in this study. The hybrid coupling beam couples the wall limbs by a friction damper connected through steel beam segments. The strength and stiffness of the friction damper are carefully designed to concentrate more deformation in the damper. The friction mechanism could dissipate more energy than the traditional RC coupling beam. And the uncertainties introduced by the design process and the inherent characteristics of traditional RC coupling beams or other types of dampers are significantly reduced. High-strength bolts are used for all connections, so that it could be quickly replaced once any damage is observed after an earthquake. In this study, a friction damper using semi-metallic friction plates and stainless-steel shims as the contact pair was tested at different loading rate. The temperature was measured. A thermal-mechanical model was then developed to correlate the dissipated energy with the friction coefficient or friction force, which can be easily incorporated into the structural design process. Finally, the hybrid coupling beam was designed and tested quasi-statically. The force, deformation, and energy dissipation capacity were compared with the traditional RC coupling beam, which also demonstrated the damage controllability by using the propose hybrid coupling beam.

Seismic performance of special RC coupling beams with modified diagonally oriented reinforcement

Seismic performance of special RC coupling beams with modified diagonally oriented reinforcement

Integrating of Nonlinear Shear Models into Fiber Element for Modeling Seismic Behavior of Reinforced Concrete Coupling Beams, Wall Piers, and Overall Coupled Wall Systems

Reinforced concrete (RC) coupled wall systems, compared with RC shear wall without opening, have more complex nonlinear behavior under the extreme earthquake loads due to the existence of coupling beams. The behavior characteristics induced by nonlinear shear deformation such as shear–flexure interaction, pinching effect, strength and stiffness deterioration are clearly observed in numerous cyclic tests of RC coupling beams and shear walls. To develop an analytical model capable of accurately and efficiently assessing the expected seismic performance of RC coupled wall systems, it is critical to define the appropriate key components models (i.e., nonlinear models of RC wall piers/shear walls and coupling beams). Classic fiber beam element based on the theory of Euler–Bernoulli beam is frequently adopted to simulate the nonlinear responses of slender RC wall piers and coupling beams in the literature because it is able to accurately model the response characters from interaction of axial–bending moment at the section level. However, classic fiber beam element cannot capture the nonlinear behaviors of non-slender structures mainly controlled by nonlinear shear deformation. To overcome this shortcoming, a modified force-based fiber element (MFBFE) including shear effect is introduced and used as the analysis element of non-slender RC coupling beams and shear walls. At the section level, a novel shear model for RC coupling beams and an existed shear model for RC shear walls are respectively added to this fiber element to simulate nonlinear responses of these two key components. The analytical model for RC coupled walls hence is formed through integrating the proposed models of these two key components. The validations with different experimental results of cyclic tests including key components and structural system reported in the literature using these proposed models are performed. Good agreements are achieved for all of these proposed models via comparisons between predicted results and experimental data.

Shear behavior of slender geometry RC coupling beams in seismic response

Coupling beams have geometric sizes with special heights known as deep beams, and the design usually takes up more space. Focus of this research is to analyze slender coupling beams with a diagonal reinforcement angle design of less than 20 degrees to the longitudinal reinforcement. New alternative design for slender coupling beams was experimentally investigated where the parameter was the span-to-depth ratios (2.75; 3.0; 3.25). Coupling beams should not be considered as load receiver, but instead as connector between the couple shear walls for working together. The result of the test indicated that coupling beams with a slenderness ratio of 3.25 has capacity to behave as coupling beams which function is to distribute the energy.