간접하중을 받는 깊은 보의 전단거동에 관한 실험적 연구

이진섭(Lee, Jin-Seop) 대한건축학회 2013 大韓建築學會論文集 : 構造系 Vol.29 No.3

Reinforced concrete deep beams have many useful applications in building structures such as transfer girders, wall footings, and foundation pile caps. Particularly, the use of the deep beams at the lower levels in tall buildings for both residential and commercial purposes has been increased rapidly because of their conveniences and economical efficiencies. Generally, this system consists of two types of deep beams. One is a beam that is directly resisting vertical load from columns and walls. The other type resists the shear force transferred from the transverse deep beams which are subjected to vertical loads directly. The shear strength of this type of beams cannot be predicted by conventional shear strength equations because of the different loading conditions and internal stress transfer mechanisms. The purpose of this study is to experimentally investigate the shear transfer mechanisms of “Indirectly Loaded Deep Beam”. The test results showed that the “Indirectly Loaded Deep Beams” had the almost identical shear strengths with the directly top-loaded deep beam. However, as the shear span to effective depth ratio of transverse beam was increased as 0.5, 1.0, and 1.5, the deflection at maximum load was increased 1.23, 1.67, and 2.17 times respectively. If the system consists of two perpendicular deep beams with same depth, the shear behavior of indirectly loaded deep beams can be explained using the three dimensional strut and tie model with a stress transfer node in a joint region.

Shear strength estimation of RC deep beams using the ANN and strut-and-tie approaches

Gunnur Yavuz 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.57 No.4

Reinforced concrete (RC) deep beams are structural members that predominantly fail in shear. Therefore, determining the shear strength of these types of beams is very important. The strut-and-tie method is commonly used to design deep beams, and this method has been adopted in many building codes (ACI318-14, Eurocode 2-2004, CSA A23.3-2004). In this study, the efficiency of artificial neural networks (ANNs) in predicting the shear strength of RC deep beams is investigated as a different approach to the strut-and-tie method. An ANN model was developed using experimental data for 214 normal and high-strength concrete deep beams from an existing literature database. Seven different input parameters affecting the shear strength of the RC deep beams were selected to create the ANN structure. Each parameter was arranged as an input vector and a corresponding output vector that includes the shear strength of the RC deep beam. The ANN model was trained and tested using a multi-layered back-propagation method. The most convenient ANN algorithm was determined as trainGDX. Additionally, the results in the existing literature and the accuracy of the strut-and-tie model in ACI318-14 in predicting the shear strength of the RC deep beams were investigated using the same test data. The study shows that the ANN model provides acceptable predictions of the ultimate shear strength of RC deep beams (maximum R2≈0.97). Additionally, the ANN model is shown to provide more accurate predictions of the shear capacity than all the other computed methods in this study. The ACI318-14-STM method was very conservative, as expected. Moreover, the study shows that the proposed ANN model predicts the shear strengths of RC deep beams better than does the strut-and-tie model approaches.

Experimental and numerical investigations on reinforcement arrangements in RC deep beams

Husem, Metin,Yilmaz, Mehmet,Cosgun, Suleyman I. Techno-Press 2022 Advances in concrete construction Vol.13 No.3

Reinforced concrete (RC) deep beams are critical structural elements used in offshore pile caps, rectangular cross-section water tanks, silo structures, transfer beams in high-rise buildings, and bent caps. As a result of the low shear span ratio to effective depth (a/d) in deep beams, arch action occurs, which leads to shear failure. Several studies have been carried out to improve the shear resistance of RC deep beams and avoid brittle fracture behavior in recent years. This study was performed to investigate the behavior of RC deep beams numerically and experimentally with different reinforcement arrangements. Deep beams with four different reinforcement arrangements were produced and tested under monotonic static loading in the study's scope. The horizontal and vertical shear reinforcement members were changed in the test specimens to obtain the effects of different reinforcement arrangements. However, the rebars used for tension and the vertical shear reinforcement ratio were constant. In addition, the behavior of each deep beam was obtained numerically with commercial finite element analysis (FEA) software ABAQUS, and the findings were compared with the experimental results. The results showed that the reinforcements placed diagonally significantly increased the load-carrying and energy absorption capacities of RC deep beams. Moreover, an apparent plastic plateau was seen in the load-displacement curves of these test specimens in question (DE-2 and DE-3). This finding also indicated that diagonally located reinforcements improve displacement ductility. Also, the numerical results showed that the FEM method could be used to accurately predict RC deep beams'behavior with different reinforcement arrangements.

깊이 1200mm급 변단면보의 중간모멘트골조용 내진접합부 개발

정시화,알미아이유 로벨 원디므,박만우,주영규 대한건축학회 2019 大韓建築學會論文集 : 構造系 Vol.35 No.4

Deep beam has high section modules compared with shallow beam of the same weight. However, deep beam has low rotational capacity and high possibility of brittle failure so it is not possible to apply deep beams with a long span to intermediate moment frames, which should exhibit a ductility of 0.02rad of a story drift angle of steel moment frames. Accordingly, KBC and AISC limit the beam depth for intermediate and special moment frame to 750mm and 920mm respectively. The purpose of this paper is to improve the seismic performance of intermediate moment frame with 1200mm depth beam. In order to enhance vulnerability of plastic deformation capacity of deeper beam, Multi-Reduced Taper Beam(MRTB) shape that thickness of beam flange is reinforced and at the same time some part of the beam flange width is weakened are proposed. Based on concept of multiple plastic hinge, MRTB is intended to satisfy the rotation requirement for intermediate moment frame by dividing total story drift into each hinge and to prevent the collapse of the main members by inducing local buckling and fracture at the plastic hinge location far away from connection. The seismic performance of MRTB is evaluated by cyclic load test with conventional connections type WUF-W, RBS and Haunch. Some of the proposed MRTB connection satisfies connection requirements for intermediate moment frame and shows improved the seismic performance compared to conventional connections. 본 연구에서는 보 깊이 1200mm의 중간모멘트골조 접합부를 개발하여 기존 철골 중간모멘트골조의 회전 성능을 향상시키고자 하였다. 깊은 보가 가지는 취약한 소성변형능력을 향상시키고자 보의 휨거동에 기반한 MRTB 접합부를 제안하였고, 제안된 접합부들의 내진 성능은 기존 접합부들과 함께 반복가력실험을 수행하여 평가하였다. MRTB 접합부는 중간모멘트골조 요구 성능을 만족하며 기존 접합부들 보다 향상된 회전 성능을 나타내었고, MRTB 형상별 거동 특성 차이를 나타내었다.

Strut-tie model for two-span continuous RC deep beams

Chae, H.S.,Yun, Y.M. Techno-Press 2015 Computers and Concrete, An International Journal Vol.16 No.3

In this study, a simple indeterminate strut-tie model which reflects complicated characteristics of the ultimate structural behavior of continuous reinforced concrete deep beams was proposed. In addition, the load distribution ratio, defined as the fraction of applied load transferred by a vertical tie of truss load transfer mechanism, was proposed to help structural designers perform the analysis and design of continuous reinforced concrete deep beams by using the strut-tie model approaches of current design codes. In the determination of the load distribution ratio, a concept of balanced shear reinforcement ratio requiring a simultaneous failure of inclined concrete strut and vertical steel tie was introduced to ensure the ductile shear failure of reinforced concrete deep beams, and the primary design variables including the shear span-to-effective depth ratio, flexural reinforcement ratio, and compressive strength of concrete were reflected upon. To verify the appropriateness of the present study, the ultimate strength of 58 continuous reinforced concrete deep beams tested to shear failure was evaluated by the ACI 318M-11's strut-tie model approach associated with the presented indeterminate strut-tie model and load distribution ratio. The ultimate strength of the continuous deep beams was also estimated by the experimental shear equations, conventional design codes that were based on experimental and theoretical shear strength models, and current strut-tie model design codes. The validity of the proposed strut-tie model and load distribution ratio was examined through the comparison of the strength analysis results classified according to the primary design variables. The present study associated with the indeterminate strut-tie model and load distribution ratio evaluated the ultimate strength of the continuous deep beams fairly well compared with those by other approaches. In addition, the present approach reflected the effects of the primary design variables on the ultimate strength of the continuous deep beams consistently and reasonably. The present study may provide an opportunity to help structural designers conduct the rational and practical strut-tie model design of continuous deep beams.

Tests of reinforced concrete deep beams

Wen-Yao Lu,Hsin-Tai Hsiao,Chun-Liang Chen,Shu-Min Huang,Ming-Che Lin 사단법인 한국계산역학회 2015 Computers and Concrete, An International Journal Vol.15 No.3

This study reports the test results of twelve reinforced concrete deep beams. The deep beams were tested with loads applied through and supported by columns. The main variables studied were the shear span-to-depth ratios, and the horizontal and vertical stirrups. The shear strengths can be effectively enhanced for deep beams reinforced with both horizontal and vertical stirrups. The test results indicate the shear strengths of deep beams increase with the decrease of the shear span-to-depth ratios. The normalized shear strengths of the deep beams did not increase proportionally with an increase in effective depth. An analytical method for predicting the shear strengths of deep beams is proposed in this study. The shear strengths predicted by the proposed method and the strut-and-tie model of the ACI Code are compared with available test results. The comparison shows the proposed method can predict the shear strengths of reinforced concrete deep beams more accurately than the strut-and-tie model of the ACI Code.

Hysteretic Behavior of Conventionally Reinforced Concrete Coupling Beams in Reinforced Concrete Coupled Shear Wall

Soo-Yeon Seo,Hyun-Do Yun,Young-Soo Chun 한국콘크리트학회 2017 International Journal of Concrete Structures and M Vol.11 No.4

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.

Behaviour of Steel Deep Beams in Moment Frames with Web Opening Subjected to Lateral Loading

Masoud Hoseinzadeh Asl,Maryam Jahanian 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.5

Due to the sharp change of the lateral load moment diagram in deep beams, the commonly proposed rigid connections may be incapable of proper transferring the plastic region away from the connection face into the beam. That is why prequalifi ed connections of steel moment frames, proposed by diff erent design codes, impose geometrical limitations on the beam spanto- depth ratio, which limits the application of the prequalifi ed connections for short deep beams. The aim of this paper is to suggest details on leading the plastic area away from the column face by making a rectangular web opening at the mid-span of the deep beam. In order to stabilize the weakened area, stiff eners are used around the opening. 52 fi nite element models of deep beams with diff erent geometries of the web openings are investigated. The results show that the use of deep beams with web opening located at mid-span in a steel moment frame is an effi cient method to relocate the plastic hinge away from the connections, resulting in increased ductility. A parametric study is carried out on the eff ect of stiff eners dimensions, web thickness, and corner radius of web opening on behavior of deep beams in moment frames. A step-by-step design algorithm is also propounded for detailing of the web opening and the stiff ener size.

연화 스트럿-타이 모델에 의한 고강도 철근콘크리트 깊은 보의 전단강도 예측에 관한 연구

김성수 ( Kim Seong-soo ),이우진 ( Lee Woo-jin ) 한국구조물진단유지관리공학회 2003 한국구조물진단유지관리공학회 논문집 Vol.7 No.4

춤이 깊은 보 설계를 위한 현행 ACI 기준은 콘크리트 압축강도 4()MPa이하의 실험결과를 바탕으로 한 반경험적인 제안식으로서 40MPa이상 고강도콘크리트의 사용이 증가됨에 따라 현행 기준의 고강도 깊은 보에 대한 적용성 평가가 요구되고 있다. 고강도 깊은 보의 전단강도 예측을 위하여 본 연구에서는 콘크리트강도와 모멘트효과를 고려한 수정 연화 스트럿-타이 모델을 제시하였다. 제안모델 평가를 위하여 4개의 시험체를 제작하였으며, 콘크리트 압축강도 49~78MPa로 제작된 74개의 기존 실험 데이터를 적용하여 ACI 318-99 11.8기준, ACI 318-02 부록 A STM의 해석결과와 비교 · 평가하였다. In the ACI Code, the empirical equations governing deep beam design are based on low-strength concrete specimens with fck in the range of 14 to 40MPa. As high-strength concrete(HSC) is becoming more and more popular, it is timely to evaluate the application of HSC deep beam. For the shear strength prediction of HSC deep beams, this paper proposed Softened Strut-and-Tie Model (SSTM) considered HSC and bending moment effect. The shear strength predictions of the proposed model, the Appendix A Strut-and-Tie Model of ACI 318-02, and Eq. of ACI 318-99 11.8 are compared with the experimental test results of 4 deep beams and the collected experimental data of 74 HSC deep beams, compressive strength in the range of 49~78MPa. The proposed SSTM performance consistently reproduced 74 HSC deep beam measured shear strength with reasonable accuracy for a wide range of concrete strength, shear span-depth ratio, and ratio of horizontal and vertical reinforcement.

An Experimental Study on the Shear Strengthening of Reinforced Concrete Deep Beams with Carbon Fiber Reinforced Polymers

Muhammad Afaq Javed,Muhammad Irfan,Sumera Khalid,Yulong Chen,Saeed Ahmed 대한토목학회 2016 KSCE Journal of Civil Engineering Vol.20 No.7

In recent years, Fiber Reinforced Polymers (FRP) have emerged as useful materials for structural strengthening and rehabilitation. The main aspire of this research is towards evaluating the efficiency of Carbon Fiber Reinforced Polymers (CFRP) in enhancing the shear strength of deep beams. The research work included construction and testing of eight (08) reinforced concrete deep beams. Two of the beams, designated as control beams, were without any shear reinforcement. Remaining six beams were divided into three groups, with each group having two identical beams. Beams in one of these groups were strengthened with conventional type of steel web reinforcement. Remaining two groups were strengthened externally by CFRP sheets with different orientations of CFRP. Magnitude of load causing shear cracks to initiate, and the failure load of each beam was recorded. Significant increase in overall load carrying capacities was observed with both CFRP sheets and web steel reinforcement. CFRP was found to be considerably effective in delaying the initial appearance of shear cracks, thereby improving the serviceability limit state of beams. Beams with CFRP orientation perpendicular to the shear cracks showed higher increment in shear strength. In conclusion, CFRP laminates could effectively be used to strengthen existing RC structures deficient in shear strength, and also to reduce/replace internal steel web reinforcement in new RC structures. Material cost comparison of CFRP reinforced beams with conventional web reinforcement is presented, and the general cost effectiveness of structural rehabilitation by means of CFRP is also discussed.