Diagonal Reinforcement Research Articles

Crashworthiness of tapered thin-walled S-shaped structures

In a vehicular crash, a higher level of energy absorption in the frontal structures of the vehicle leads to less transferred energy to the passengers and less possibility for injury. S-shaped front rails, also known as S-rails, are one of the main structural elements and energy absorbers in the body of a vehicle. To improve the safety of passengers, the S-rail design should be optimized to absorb higher levels of energy in a frontal crash. In this study, the impact of tapering S-rails on the energy absorption is investigated. Two S-rails, one without internal diagonal reinforcement (type-A) and one with internal diagonal reinforcement (type-B), are both tapered with 20 different tapering ratios ranging from 110% to 300% in 10% increments. All of the S-rail models are subjected to static and dynamic loading conditions. Finite element analysis is used to assess the effectiveness of tapering S-rails by investigating the energy absorption (EA) and specific energy absorption (SEA) variations. An equation is developed to verify the numerical results. In this study, the reinforcing and tapering S-rails are shown to improve the EA and SEA under both static and dynamic loading conditions. By combining reinforcing and tapering techniques, S-rails showed a noticeable improvement in SEA of more than 300% in the static loading condition and an improvement of 275% in the dynamic loading condition.

Numerical study of shear wall behavior coupled with HPFRCC beam and diagonal reinforcements

Article history: Received 6 September, 2015 Accepted 20 December 2015 Available online 21 December 2015 High performance fiber-reinforced cementitious composites (HPFRCC) are aggregates like cement grout with fine grains and fibers which can be used in many cases like seismic improvement of building components. One of these building components is connecting beam in coupled shear wall which can increase plasticity and energy absorption. In this paper nonlinear finite element model of coupled beam containing HPFRCC is analyzed and the influence diagonal reinforcement is investigated on cracking patterns, stress contours and hysteresis diagrams of shear wall. It was observed that diagonal reinforcements play significant role in shear load bearing capacity of shear wall coupled with HPFRCC beam. © 2016 Growing Science Ltd. All rights reserved.

On the definition deflections of monolithic slabs with the mixed reinforcing at the stage of limit equilibrium

The article considers innovative materials and structures for flat monolithic slabs. Overlapping mixed diagonal reinforcement where high strength is used as prestressing reinforcement in a flexible sheath type “Monostrend”. The article discusses the theoretical solution to determine the deflection of a monolithic beamless slab without capitals in the process of limiting equilibrium. The formula based on the value of the limiting deflection cell, reinforcement class and plate thickness. Shows a plot of marginal values of deflections of different thickness slabs with reinforcement A500, for three cells to span 6, 7 and 9 m. These data set the initial stress in high-strength reinforcement and stress as a result acquired deflection in the slab floors with mixed diagonal reinforcement.

묶음 대각철근을 갖는 세장한 철근콘크리트 연결보의 이력거동

묶음 대각철근을 갖는 세장한 철근콘크리트 연결보의 이력거동

Behaviour of fibre-reinforced beams with diagonal reinforcement

Diagonal reinforced coupling (DRC) beams can provide excellent strength, stiffness and energy dissipation capacities. However, fabricating DRC beams at construction sites is difficult due to reinforcement congestion and interference among the reinforcements due to the complex arrangement required by current design provisions. The objective of this study is to simplify the reinforcement details of DRC beams by reducing the transverse reinforcement around the beam perimeter that is required for the confinement of DRC beams. This is achieved by using high-performance fiber-reinforced cement composites (HPFRCC) for DRC beams. Experiments are conducted using six specimens under reversed cyclic loads to evaluate the hysteretic behaviours of the HPFRCC DRC beams. The test results show that the use of HPFRCC in DRC beams is very effective, providing a confinement effect with transverse reinforcement. HPFRCC DRC beams with half the transverse reinforcement required by ACI 318-11 provide almost identical energy dissipation capacities as concrete DRC beams detailed according to ACI 318-11.

보-기둥 접합부의 방폭성능에 관한 해석적 연구

폭발사고나 테러 등이 증가함에 따라 구조물 방폭성능의 요구가 증가되고 있다. 국내에서도 폭발사고 등에 대비하기 위한 방폭구조물의 수요가 증가할 것이며, 이를 위해서는 다양한 측면의 관련 연구가 수행되어야 할 것이다. 본 연구에서는 철근상세가 보-기둥 접합부의 방폭성능에 미치는 영향에 대해 분석하였다. 표준 시험체는 보-기둥 설계매뉴얼을 바탕으로 정하중에 대해 설계되었으며 이 외에 철근상세에 따른 영향을 분석하기 위해 휨, 전단, Diagonal철근 등이 보강된 시험체와 비교하였다. 접합부의 방폭성능을 평가하기 위해 유한요소해석 프로그램인 LS-DYNA에 의한 해석적 연구가 수행되었다. 해석결과는 시험체의 파괴형상, 변형, 지점회전각 그리고 철근의 응력을 포함하고 있다. 추가적인 휨철근이 보강된 시험체의 방폭성능을 표준 시험체와 비교하여 큰 차이를 보이지 않았으나, Diagonal철근이 보강된 시험체는 보 영역에서 발생하는 소성힌지영역을 이동시켜 접합부의 안전성을 확보하는 등 방폭성능을 향상시켰다. 따라서 동일한 철근비에서 휨철근보다 Diagonal철근이 폭발하중에 더 효율적으로 저항하는 것을 확인하였다. 이에 더하여 전단철근이 배근된 시험체는 우수한 방폭성능을 보였으며, 이를 통해 폭발하중을 받는 콘크리트 구조에서 휨 성능과 함께 전단성능 역시 중요한 고려사항임을 확인할 수 있었다. As the increase of explosive accidents and terrorism, demands of blast-resistant capacity in structures would be increased to prevent those situation. Therefore, various studies on blast-resistant structures should be performed. In this study, behavior of beam-column connections is investigated. Base specimen was designed according to the design criterion of beam-column connections. To determine the effects of reinforcement details, flexure, shear and diagonal bar were considered as variables. LS-DYNA, nonlinear finite element program, is selected to the numerical analysis of specimens. The analysis results included failure shape of specimens, deflection, support rotation and stress of reinforcements. In conclusion, specimen which was reinforced with additional flexure bars did not show significant differences as contrasted with base specimen. The diagonal reinforcements are more effective to resist the blast loads than additional flexure reinforcements because safety of connection was enhanced due to the transfer of plastic hinge region in case of reinforcing diagonal bars. In the specimen which is reinforced with additional shear bars, outstanding behavior was observed. In the structures subjected to blast loads, therefore, it is should be considered to not only flexural performance but also shear forces.

강섬유와 묶음철근 보강을 통한 고성능 연결보의 이력거동 평가

In this paper, a bundled diagonal reinforcement using high performance steel fiber was proposed to enhance the construct ability and seismic performance. Experiments of coupling beam was composed of four specimens and the hysteretic behavior evaluated for reverse cyclic loading to specimens using high performance steel fiber. The main variables of the experiment is a amount of stirrup and bundled reinforcement, depending on whether the mix of steel fiber. Specimen which criteria was applied 100% of stirrup and bundled diagonal reinforcement of ACI318 criteria. With this, by appling same diagonal reinforcement, two specimens were created by adjusting stirrup of 75%, 50%. So, a total of four specimens were produced. When coupling beam was placed concrete, this experiment was mixed in a content of steel fiber 1%. All the specimens were produced by aspect ratio 3.5(l/h=1050/300) to a half-scale. In this result, two specimens as reduced to stirrup of 75%, 50% was no significant difference in the strength, stiffness and energy dissipation capacity, respectively compared to the stirrup of 100%.

Cyclic performance of precast coupling beams with bundled diagonal reinforcement

Diagonally reinforced coupling beams designed according to current codes are expected to endure significant inelastic deformations during earthquakes. However, it is very difficult to fabricate the coupling beams in a construction site due to the congestion of reinforcement and the complex arrangement of diagonal reinforcement. For resolving the problems, this study developed precast coupling beams with bundled diagonal reinforcement. To verify the effectiveness of the proposed design method, experimental tests were conducted on four 1/2-scale coupling beam specimens subjected to cyclic loading. The test results suggest that the precast coupling beams with bundled diagonal reinforcement exhibited good ductility and energy dissipation capacities similar to those having code-specified diagonal reinforcement.

보강상세에 따른 특수전단벽 연결보의 내진성능

(Received November 28, 2014 / Revised January 28, 2015 / Accepted January 29, 2015)iŠ´geA o ¼C £©€ a ae `ICAE C± a cE3 , 3 ¨ , aoCU ! o €‰E × . IMl - c #' 2.0 2C 4e( Ÿ ׳ 6½ !4AI a bUa´geA 5±´ge e×o” 3 , 3 ¨ , ´ ¨CU !4Z#Je( Ÿ ׳ 6½ ƒ aA~© c ˜Uu 2³ E× . i´œ© ›A 2CE‚ j©eE Ð gor -C Jae ›e( Ÿ×³ 6½ ƒ a e <CAE Eer ƒ aE 2 a a ae´ œ#¤× . ag€ , ˆ?o þaee3$ SA a <'e(oUe3½ !× bM jKE SB $ ² -a <O #—C±or h$K !e¼ ] , AE | -e( Ÿ×³ 6½ ƒ a 4ACA a <O #—C±  wE3 , 3 ¨ , ©j o A zCU€aoCU (drift) !J o[¤× . š j˜  I a bUa´ge , e3 ƒ a , [ ¼ ¨CABSTRACTCoupling beams posses proper strength, stiffness and ductility capacities to resist efficiently under seismic loads. The strength, stiffness and ductility capacities for special diagonally reinforced concrete coupling beam with a span-to-depth ratio 2.0 or less is higher than those of coupling beam with conventionally reinforced concrete coupling beam. However, diagonally reinforced detailing creates major construction problem. In this study, design alternatives for diagonally reinforced concrete coupling beams were experimentally investigated. The results show that angle reinforced coupling beam(specimen SA) exhibited a better stable behavior in comparison with non-diagonally coupling beams(specimens SB-series) and sustained corresponding drift ratio, peak-to-peak stiffness and cumulative dissipated energy in comparison to diagonally coupling beam(specimen CA). ,FZXPSET Special Diagonally Reinforced Concrete Coupling Beam, Reinforcement Detail, Seismic Performance

FRP as strengthening material for Reinforced Concrete beams with openings — A review

This paper presents the review of studies performed to investigate the behavior of Reinforced Concrete (RC) beams containing different types of openings. For the last 4 decades, research works involved the investigation of the member strength and development of the design approach for simply supported, continuous and T-beams containing large rectangular openings subjected to torsion, bending and shear forces. The proposed design method suggested the installation of diagonal steel reinforcement bars around the opening for providing the required strength. In recent years, Fiber Reinforced Polymers (FRP) have been widely used as an external bonded reinforcement system for upgrading and retrofitting of concrete structures. FRP as externally bonded reinforcement mainly used to repair and retrofit the damaged reinforced concrete member. However, very limited studies showed the application of the FRP laminates as external reinforcement around openings. Therefore, further investigations regarding the application of FRP laminates to strengthen the large openings in reinforced concrete members are very vital.

Effective stiffness of reinforced concrete coupling beams

Reinforced concrete (RC) structural walls with coupling beams are widely used as the primary lateral-load-bearing elements in high-rise building structures. Many researches have shown that there is uncertainty in the estimation of the effective stiffness of RC coupling beams. In an attempt to develop rational approaches regarding the stiffness of these structural components, this paper presents the analytical approaches, considering the influence of flexural and shear deformations, to determine the effective stiffness of RC coupling beams. A comprehensive parametric study, including 144 combinations for the conventionally reinforced concrete coupling beam (CCB) and 48 combinations for the diagonally reinforced concrete coupling beam (DCB), is carried out and two equations to estimate the effective stiffness of RC coupling beams are proposed each as a function of aspect ratio, transverse reinforcement ratio, longitudinal reinforcement ratio, diagonal reinforcement ratio and concrete compressive strength, on the basis of these parametric case studies. The proposed analytical approaches and the equations for assessing the effective stiffness of CCBs and DCBs are then verified by comparison with experimental results obtained from literature.

Effectiveness of high performance fiber-reinforced cement composites in slender coupling beams

This study aims at exploring the use of high performance fiber-reinforced cement composites (HPFRCCs) as an innovative method of improving the seismic performance of slender coupling beams. Also, the effect of diagonal reinforcement in slender coupling beams is evaluated in comparison to conventional reinforcement. Three 1/2-scale coupling beams having the length-to-depth ratio of 3.5 were tested under cyclic lateral loading up to about 10% drift. The key test variables were material type and reinforcement layout. For the material type, normal concrete and HPFRCC using PVA discrete fibers of 2% volumetric ratio were compared. The mix proportions of the HPFRCC were determined through detailed material tests. Two types of reinforcement layout were tested: conventional and diagonal layout. Furthermore, the strength and stiffness characteristics of reinforced concrete or HPFRCC coupling beams are examined by assembling a database of almost all coupling beam tests available in literature.

묶음 대각철근을 적용한 철근콘크리트 연결보의 이력거동 평가

Diagonal reinforced coupling beam of coupled shear walls can provide sufficient strength and stiffness to resist lateral force. However, the reinforcement details for coupling beams required by ACI 318 (2011) are difficult to construct because of the reinforcement congestion and confined interior area. This study presents experimental results about the seismic performance of coupling beams having bundled diagonal reinforcement to improve the workability. Experiments were conducted using half scaled precast coupling beams having an aspect ratio of 2.0. It was observed that the bundled diagonal reinforced coupling beams can develop seismic performance similar to the coupling beams with requirement details specified in ACI 318 (2011).

Flexural behavior of RC beams with regular square or circular web openings

This paper presents a study aimed at investigating the influence of multiple web openings along the length of an RC beam on its flexural behavior. A total of nine rectangular beams were tested. Diagonal reinforcement around openings effectively prevented premature failure of some specimens due to Vierendeel action, the expected failure mode according to bending moment-axial force interaction diagrams. Longitudinal rebars and full-depth stirrups adjacent to openings and short stirrups in the chords prevented beam-type and frame-type shear failures. The length of the plastic failure mechanism increased in the presence of multiple openings compared to beams with a single opening.

The Effect of Alternative Reinforcement Details in Reinforced Concrete Coupling Beams

In this study, a design alternative for reinforced concrete (RC) coupling beamswith diagonal headed-bars that puts less reliance on diagonal reinforcement wasexperimentally investigated. The results show that specimen HB 50 exhibits a better stable behavior incomparison with specimens CON and HB 30. Test results showed that specimens HB75 with replacement ratio of 75 % diagonal headed – bars were efficient inresisting high shear load.

Finite Element Analysis of High-Strength Concrete Flat Columns with Diagonal Reinforcements

Based on the reversed cyclic loading test of three 1:4 high-strength concrete flat columns, the computer program ABAQUS was used to simulate behaviors of the specimens. Concrete in the column was modeled using the damage plasticity material model, and a uniaxial steel model with combined isotropic and kinematic hardening properties was used to simulate the behavior of the reinforcement. The establishment of the finite element model, definition of the material parameters and the influence of diagonal reinforcement were discussed at length. The results show that the concrete damage plasticity model can be well used for hysteretic analysis of reinforced concrete members if the relevant parameters are reasonably defined. Diagonal reinforcements can not significantly improve ductility of the specimens, but can improve their shear capacities. This paper can provide reference for the performance simulation of reinforced concrete members under cyclic loading.

Seismic assessment of existing RC shear walls non-compliant with current code provisions

This work forms part of a research programme to assess and strengthen existing reinforced concrete (RC) walls that were designed using older seismic codes. The main object of the present paper is to examine the behaviour of concrete shear walls that do not comply with modern seismic codes (Eurocode 2 (EC2) and Eurocode 8 (EC8)) and compare their experimental performance with the provisions for assessment of RC members included in EC8 Part 3. For this purpose, a series of six shear walls (height h = 1·40 m, length l = 0·74 m, thickness b = 0·10 m) was designed and tested under static cyclic loading. The wall specimens were characterised by various types of reinforcement arrangement, focusing on different amounts of shear reinforcement. The issues investigated are the failure modes, ductility level, the absence of confined boundary elements, the low amount of shear reinforcement, the influence of diagonal reinforcement and the influence of axial load. The experimental results are compared with the provisions included in EC8 Part 3, which predict the shear strength, the chord rotation ductility and the effective stiffness of RC shear walls.

단차가 있는 철근콘크리트 슬래브의 구조성능 평가 실험 및 상세 제안

이 실험적 연구는 콘크리트 단차슬래브의 성능을 평가하고 단차가 없는 평슬래브와 동등한 휨강도를 발현할 수 있는 보강상세를 제안하는데 그 목적이 있다. 이 연구에서는 단순지간 4점 재하 실험을 통하여 다양한 보강상세를 가진 12개 실험체의 성능을 서로 비교하였다. 추가보강근이 없는 단차슬래브는 휨강도, 강성, 처짐, 균열 등에서 평슬래브와 비교하여 매우 낮은 성능을 가졌으며, 특히 단차 내에서 균열이 빠르게 진전되어 조기에 힌지현상이 발생하였다. 반면 역U형철근, U형철근, 역L형철근, L형철근 등의 추가 보강상세를 가지는 단차슬래브는 평슬래브와 동등한 휨강도를 발현하였다. 역U형철근과 U형철근은 단차의 사인장 균열을 제어하는데 효과적이었고, 역L형철근과 L형철근은 일관적으로 단차 밖 평슬래브로 슬래브 주근의 휨항복을 유도하는 것으로 나타났다.

Shear Capacity of Reinforced Concrete Beam with Diagonal Reinforcement Based on Modified Compression Field Theory

AbstractFor the compression—shear failure of a reinforced concrete bridge beam with diagonal reinforcement, the calculation of ultimate shear capacity is proposed based on the modified compression field theory (MCFT). Shear force is shared by the shear compression zone of concrete, stirrups, and diagonal reinforcements intersecting with diagonal cracks. The shear capacities of concrete in the tensile and compression areas are calculated. The new balance equation between the average stress and the internal force of cracked concrete is established, and the effects of diagonal reinforcement on the stress of diagonal cracks are considered. This procedure considers the constitutive relation conditions of materials and the deformation compatibility of concrete. The theoretical shear capacity predicted by MCFT is validated by the test results of two reinforced concrete beams, providing a reference for calculating the capacity of reinforced concrete beam.

Experimental investigation on reinforced concrete interior beam–column joints rehabilitated by ferrocement jackets

In this study, a method for rehabilitating reinforced concrete interior beam–column joints using ferrocement jackets with embedded diagonal reinforcements is proposed. It improves seismic performance of substandard beam–column joints and repairs deteriorated concrete cover without increasing the dimensions of the joints. Ferrocement, comprising mortar and wire mesh, was applied to replace concrete cover to enhance shear strength of the joints. Diagonal reinforcements were installed to reduce the forces transferred to the joint core. Four 2/3 scale interior beam–column joints, including one control specimen and three strengthened specimens, were prepared and tested under quasi-static cyclic loading. Three types of mortars were considered for each strengthened specimen. Test results have indicated that the proposed rehabilitation method can improve seismic performance of interior beam–column joints using ferrocement with high strength mortar. Strength of mortar is the vital factor affecting the performance of strengthened specimens. Anchor bolts installed at the interface between ferrocement and concrete substrate improve bonding and overall performance. Finally, a method for predicting the shear strength of joints rehabilitated by ferrocement jackets with embedded diagonal reinforcements is proposed.