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Dynamic analyses of steel-reinforced super high-strength concrete columns

JIA Jinqing, JIANG Rui, XU Shilang, HOU Tong

《结构与土木工程前沿（英文）》 2007年 第1卷 第2期   页码 240-246 doi: 10.1007/s11709-007-0030-2

摘要： The dynamic behaviors of steel-reinforced super high-strength concrete columns under seismic loading were studied with a series of experiments. Thirteen specimens, with concrete strengths ranging from 94.9 to 105.4 MPa and shear-span ratios of 2.75, were manufactured. The axial load ratio and the stirrup reinforcement ratio were the main experimental variables affecting the dynamic behavior of the specimens. The columns under low cyclic lateral loading mainly failed in the flexural-shear mode. Shear force-displacement hysteretic curves and skeleton curves were drawn. The coefficients of the specimens displacement ductility were calculated. Experimental results indicate that ductility decreases while the axial load ratio increases, but it increases when the stirrup reinforcement ratio increases. The limit values of the axial load ratio and the minimum stirrup reinforcement ratio of the columns were investigated to satisfy definite ductility requirements. These values were suggested as references of engineering applications and of the amendment of the current Chinese design code of steel reinforced concrete composite structures.

关键词： amendment     flexural-shear     force-displacement hysteretic     definite ductility     skeleton    

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Uncertainty of concrete strength in shear and flexural behavior of beams using lattice modeling

《结构与土木工程前沿（英文）》 2023年 第17卷 第2期   页码 306-325 doi: 10.1007/s11709-022-0890-5

摘要： This paper numerically studied the effect of uncertainty and random distribution of concrete strength in beams failing in shear and flexure using lattice modeling, which is suitable for statistical analysis. The independent variables of this study included the level of strength reduction and the number of members with reduced strength. Three levels of material deficiency (i.e., 10%, 20%, 30%) were randomly introduced to 5%, 10%, 15%, and 20% of members. To provide a database and reliable results, 1000 analyses were carried out (a total of 24000 analyses) using the MATLAB software for each combination. Comparative studies were conducted for both shear- and flexure-deficit beams under four-point loading and results were compared using finite element software where relevant. Capability of lattice modeling was highlighted as an efficient tool to account for uncertainty in statistical studies. Results showed that the number of deficient members had a more significant effect on beam capacity compared to the level of strength deficiency. The scatter of random load-capacities was higher in flexure (range: 0.680–0.990) than that of shear (range: 0.795–0.996). Finally, nonlinear regression relationships were established with coefficient of correlation values (R2) above 0.90, which captured the overall load–deflection response and level of load reduction.

关键词： lattice modeling     shear failure     flexural failure     uncertainty     deficiency     numerical simulation    

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Enhanced empirical models for predicting the drift capacity of less ductile RC columns with flexural,shear or axial failure modes

Mohammad Reza AZADI KAKAVAND, Reza ALLAHVIRDIZADEH

《结构与土木工程前沿（英文）》 2019年 第13卷 第5期   页码 1251-1270 doi: 10.1007/s11709-019-0554-2

摘要： Capacity of components subjected to earthquake actions is still a widely interesting research topic. Hence, developing precise tools for predicting drift capacities of reinforced concrete (RC) columns is of great interest. RC columns are not only frequently constructed, but also their composite behavior makes the capacity prediction a task faced with many uncertainties. In the current article, novel empirical approaches are presented for predicting flexural, shear and axial failure modes in RC columns. To this aim, an extensive experimental database was created by collecting outcomes of previously conducted experimental tests since 1964, which are available in the literature. It serves as the basis for deriving the equations for predicting the drift capacity of RC columns by different regression analyses (both linear with different orders and nonlinear). Furthermore, fragility curves are determined for comparing the obtained results with the experimental results and with previously proposed models, like the ones of ASCE/SEI 41-13. It is demonstrated that the proposed equations predict drift capacities, which are in better agreement with experimental results than those computed by previously published models. In addition, the reliability of the proposed equations is higher from a probabilistic point of view.

关键词： flexural-shear-axial failure     drift capacity     reinforced concrete columns     statistical analysis     fragility curves    

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Flexural and longitudinal shear performance of precast lightweight steel–ultra-high performance concrete

《结构与土木工程前沿（英文）》 2023年 第17卷 第5期   页码 704-721 doi: 10.1007/s11709-023-0941-6

摘要： In this study, the flexural and longitudinal shear performances of two types of precast lightweight steel–ultra-high performance concrete (UHPC) composite beams are investigated, where a cluster UHPC slab (CUS) and a normal UHPC slab (NUS) are connected to a steel beam using headed studs through discontinuous shear pockets and full-length shear pockets, respectively. Results show that the longitudinal shear force of the CUS is greater than that of the NUS, whereas the interfacial slip of the former is smaller. Owing to its better integrity, the CUS exhibits greater flexural stiffness and a higher ultimate bearing capacity than the NUS. To further optimize the design parameters of the CUS, a parametric study is conducted to investigate their effects on the flexural and longitudinal shear performances. The square shear pocket is shown to be more applicable for the CUS, as the optimal spacing between two shear pockets is 650 mm. Moreover, a design method for transverse reinforcement is proposed; the transverse reinforcement is used to withstand the splitting force caused by studs in the shear pocket and prevent the UHPC slab from cracking. According to calculation results, the transverse reinforcement can be canceled when the compressive strength of UHPC is 150 MPa and the volume fraction of steel fiber exceeds 2.0%.

关键词： precast steel–UHPC composite beam     flexural performance     longitudinal shear performance     parametric study     transverse reinforcement ratio    

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Shear-flexural strength mechanical model for the design and assessment of reinforced concrete beams subjected

Antonio MARÍ,Antoni CLADERA,Jesús BAIRÁN,Eva OLLER,Carlos RIBAS

《结构与土木工程前沿（英文）》 2014年 第8卷 第4期   页码 337-353 doi: 10.1007/s11709-014-0081-0

摘要： A mechanical model recently developed for the shear strength of slender reinforced concrete beams with and without shear reinforcement is presented and extended to elements with uniformly distributed loads, specially focusing on practical design and assessment in this paper. The shear strength is considered to be the sum of the shear transferred by the concrete compression chord, along the crack, due to residual tensile and frictional stresses, by the stirrups and, if they exist, by the longitudinal reinforcement. Based on the principles of structural mechanics simple expressions have been derived separately for each shear transfer action and for their interaction at ultimate limit state. The predictions of the model have been compared to those obtained by using the EC2, MC2010 and ACI 318-08 provisions and they fit very well the available experimental results from the recently published ACI-DAfStb databases of shear tests on slender reinforced concrete beams with and without stirrups. Finally, a detailed application example has been presented, obtaining each contributing component to the shear strength and the assumed shape and position of the critical crack.

关键词： shear strength     mechanical model     reinforced concrete     design     assessment     shear tests    

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Strengthening of reinforced concrete beams using fiber-reinforced cementitious matrix systems fabricated with custom-designed mortar and fabrics

《结构与土木工程前沿（英文）》   页码 1100-1116 doi: 10.1007/s11709-023-0967-9

摘要： The performance of a new fiber-reinforced cementitious matrix (FRCM) system developed using custom-designed mortar and fabrics is investigated in this study. The behavior of this system is evaluated in terms of both the flexural and shear strengthening of reinforced concrete beams. Eight beams are designed to assess the effectiveness of the FRCM system in terms of flexural strengthening, and four specimens are designed to investigate their shear behavior. The parameters investigated for flexural strengthening are the number of layers, span/depth ratio, and the strengthening method. Unlike previous studies, custom fabrics with similar axial stiffness are used in all strengthening methods in this study. In the shear-strengthened specimens, the effects of the span/depth ratio and strengthening system type (fiber-reinforced polymer (FRP) or FRCM) are investigated. The proposed FRCM system exhibits desirable flexural and shear strengthening for enhancing the load capacity, provides sufficient bonding with the substrate, and prevents premature failure modes. Considering the similar axial stiffness of fabrics used in both FRCM and FRP systems and the higher load capacity of specimens strengthened by the former, cement-based mortar performs better than epoxy.

关键词： fiber-reinforced cementitious matrix     flexural strengthening     shear strengthening     carbon fiber-reinforced polymer     shear span    

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Mechanical properties characterization of different types of masonry infill walls

André FURTADO, Hugo RODRIGUES, António ARÊDE, Humberto VARUM

《结构与土木工程前沿（英文）》 2020年 第14卷 第2期   页码 411-434 doi: 10.1007/s11709-019-0602-y

摘要： It is remarkable, the recent advances concerning the development of numerical modeling frameworks to simulate the infill panels’ seismic behavior. However, there is a lack of experimental data of their mechanical properties, which are of full importance to calibrate the numerical models. The primary objective of this paper is to present an extensive experimental campaign of mechanical characterization tests of infill masonry walls made with three different types of masonry units: lightweight vertical hollow concrete blocks and hollow clay bricks. Four different types of experimental tests were carried out, namely: compression strength tests, diagonal tensile strength tests, and flexural strength tests parallel and perpendicular to the horizontal bed joints. A total amount of 80 tests were carried out and are reported in the present paper. The second objective of this study was to compare the mechanical properties of as-built and existing infill walls. The results presented and discussed herein, will be in terms of strain-stress curves and damages observed within the tests. It was observed a fragile behavior in the panels made with hollow clay horizontal bricks, without propagation of cracks. The plaster increased the flexural strength by 57%.

关键词： masonry infill walls     experimental characterization     compression strength     shear diagonal strength     flexural strength    

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Structural performance of a façade precast concrete sandwich panel enabled by a bar-type basalt fiber-reinforced polymer connector

《结构与土木工程前沿（英文）》 2023年 第17卷 第1期   页码 122-137 doi: 10.1007/s11709-022-0894-1

摘要： In this study, a novel diagonally inserted bar-type basalt fiber reinforced polymer (BFRP) connector was proposed, aiming to achieve both construction convenience and partially composite behavior in precast concrete sandwich panels (PCSPs). First, pull-out tests were conducted to evaluate the anchoring performance of the connector in concrete after exposure to different temperatures. Thereafter, direct shear tests were conducted to investigate the shear performance of the connector. After the test on the individual performance of the connector, five façade PCSP specimens with the bar-type BFRP connector were fabricated, and the out-of-plane flexural performance was tested under a uniformly distributed load. The investigating parameters included the panel length, opening condition, and boundary condition. The results obtained in this study primarily indicated that 1) the bar-type BFRP connector can achieve a reliable anchorage system in concrete; 2) the bar-type BFRP connector can offer sufficient stiffness and capacity to achieve a partially composite PCSP; 3) the boundary condition of the panel considerably influenced the out-of-plane flexural performance and composite action of the investigated façade PCSP.

关键词： precast concrete sandwich panel     basalt fiber reinforced polymer     pull-out performance     shear performance     out-of-plane flexural performance    

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Hybrid flexural components: Testing pre-stressed steel and GFRP bars together as reinforcement for flexural

Mohammed FARUQI, Oved I. MATA, Francisco AGUINIGA

《结构与土木工程前沿（英文）》 2018年 第12卷 第3期   页码 352-360 doi: 10.1007/s11709-017-0453-3

摘要：

Concrete members historically have used either pre-stressed steel or steel bars. In recent years there has been an increased interest in the use of fiber reinforced polymer (FRP) materials. However, the flexure behavior of a hybrid system reinforced by the combination of pre-stressed steel and glass fiber reinforced (GFRP) is still relatively unknown. The purpose of this work is to study this. Two slabs of 100 and 150-millimeter thickness, with a span of 2.1 m reinforced with both pre-stressing steel and GFRP were constructed and tested to failure using ACI 318-11 and ACI 440.1R-15. The concrete had strength of 31 MPa and the slabs were respectively reinforced with 5#4 bars and 3#5 bars. Each slab had 37.41 mm2 prestressing wire with a failure stress of 1722.5 MPa. The experimental flexural strength and deflection of slabs were compared with their respective sizes theoretical slabs. The theoretical slabs were either reinforced with pre-stressed steel or GFRP rebars, or a hybrid system. It was found that the hybrid system produces better results.

关键词： Partial pre-stressing     composite structures     GFRP bars    

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Analysis of stiffness and flexural strength of a reinforced concrete beam using an invented reinforcement

Nazim Abdul NARIMAN, Martin HUSEK, Ilham Ibrahim MOHAMMAD, Kaywan Othman AHMED, Diyako DILSHAD, Ibrahim KHIDR

《结构与土木工程前沿（英文）》 2021年 第15卷 第2期   页码 378-389 doi: 10.1007/s11709-021-0706-z

摘要： In this study, we conducted experimental tests on two specimens of reinforced concrete beams using a three-point bending test to optimize the flexure and stiffness designs. The first specimen is a reinforced concrete beam with an ordinary reinforcement, and the second specimen has an invented reinforcement system that consists of an ordinary reinforcement in addition to three additional bracings using steel bars and steel plates. The results of the flexure test were collected and analyzed, and the flexural strength, the rate of damage during bending, and the stiffness were determined. Finite element modeling was applied for both specimens using the LS-DYNA program, and the simulation results of the flexure test for the same outputs were determined. The results of the experimental tests showed that the flexural strength of the invented reinforcement system was significantly enhanced by 15.5% compared to the ordinary system. Moreover, the flexural cracks decreased to a significant extent, manifesting extremely small and narrow cracks in the flexure spread along the bottom face of the concrete. In addition, the maximum deflection for the invented reinforced concrete beam decreased to 1/3 compared to that of an ordinary reinforced concrete beam. The results were verified through numerical simulations, which demonstrated excellent similarities between the flexural failure and the stiffness of the beam. The invented reinforcement system exhibited a high capability in boosting the flexure design and stiffness.

关键词： three-point flexure test     softening stage     flexural crack     flexural strain    

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Effect of size on biaxial flexural strength for cement-based materials by using a triangular plate method

Hakan T TURKER

《结构与土木工程前沿（英文）》 2022年 第16卷 第8期   页码 1017-1028 doi: 10.1007/s11709-022-0871-8

摘要： The effect of size on the biaxial flexural strength (BFS) of Portland cement mortar was investigated by using the recently proposed triangular plate method (TPM). An experimental program was conceived to study the size effect by keeping a constant water-cement ratio of 0.485, cement-sand ratio of 1:2.75, and using unreinforced triangular mortar plates of five different thicknesses and seven different side lengths. The BFS of the produced specimens was tested, and variations of BFS depending on specimen thickness and side length were determined. The results indicated that increases in triangular plate specimen side length and specimen thickness led to a decrease in the BFS of Portland cement mortar. The effect of specimen length increase on BFS was more significant than on the effect of the specimen thickness. The variations in specimens’ thickness indicated a deterministic Type I size effect, while the variations in specimens’ length showed an energetic-statistical Type I size effect.

关键词： testing     apparatus & methods     plain concrete     tensile properties     biaxial flexural strength     triangular plate method    

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An experimental study on the flexural behavior of heavily steel reinforced beams with high-strength concrete

Yasser SHARIFI, Ali Akbar MAGHSOUDI

《结构与土木工程前沿（英文）》 2014年 第8卷 第1期   页码 46-56 doi: 10.1007/s11709-014-0237-y

摘要： In recent years, an emerging technology termed high-strength concrete (HSC) has become popular in construction industry. Present study describes an experimental research on the behavior of high-strength concrete beams in ultimate and service state. Six simply supported beams were tested, by applying comprising two symmetric concentrated loads. Tests are reported in this study on the flexural behavior of high-strength reinforced concrete (HSRC) beams made with coarse and fine aggregate together with Microsilica. Test parameter considered includes effect of being compressive reinforcement. Based on the obtained results, the behavior of such members is more deeply reviewed. Also a comparison between theoretical and experimental results is reported here. The beams were made from concrete having compressive strength of 66.81–77.72 N/mm and percentage reinforcement ratio ( / ) in the range of 0.56% – 1.20%. The ultimate moment for the tested beams was found to be in a good agreement with that of the predicted ultimate moment based on ACI 318-11, ACI 363 and CSA-04 provisions. The predicted deflection based classical formulation based on code provisions for serviceability requirements is found to underestimate the maximum deflection of HSC reinforced beams at service load.

关键词： high-strength concrete (HSC) members     flexural behavior     reinforced concrete     experimental results     ultimate moment    

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Effect of bond enhancement using carbon nanotubes on flexural behavior of RC beams strengthened with

《结构与土木工程前沿（英文）》 2022年 第16卷 第1期   页码 131-143 doi: 10.1007/s11709-021-0787-8

摘要： This paper studied the effect of incorporation of carbon nanotubes (CNTs) in carbon fiber reinforced polymer (CFRP) on strengthening of reinforced concrete (RC) beams. The RC beams were prepared, strengthened in flexure by externally bonded CFRP or CNTs-modified CFRP sheets, and tested under four-point loading. The experimental results showed the ability of the CNTs to delay the initiation of the cracks and to enhance the flexural capacity of the beams strengthened with CFRP. A nonlinear finite element (FE) model was built, validated, and used to study the effect of various parameters on the strengthening efficiency of CNTs-modified CFRP. The studied parameters included concrete strength, flexural reinforcement ratio, and CFRP sheet configuration. The numerical results showed that utilization of CNTs in CFRP production improved the flexural capacity of the strengthened beams for U-shape and underside-strip configurations. The enhancement was more pronounced in the case of U-shape than in the case of use of sheet strip covers on the underside of the beam. In case of using underside-strip, the longer or the wider the sheet, the higher was the flexural capacity of the beams. The flexural enhancement of RC beams by strengthening with CNTs-modified CFRP decreased with increasing the rebar diameter and was not affected by concrete strength.

关键词： RC beams     flexural     strengthening     CFRP     CNTs     finite element    

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Modeling of shear walls using finite shear connector elements based on continuum plasticity

Ulf Arne GIRHAMMAR, Per Johan GUSTAFSSON, Bo KÄLLSNER

《结构与土木工程前沿（英文）》 2017年 第11卷 第2期   页码 143-157 doi: 10.1007/s11709-016-0377-3

摘要： Light-frame timber buildings are often stabilized against lateral loads by using diaphragm action of roofs, floors and walls. The mechanical behavior of the sheathing-to-framing joints has a significant impact on the structural performance of shear walls. Most sheathing-to-framing joints show nonlinear load-displacement characteristics with plastic behavior. This paper is focused on the finite element modeling of shear walls. The purpose is to present a new shear connector element based on the theory of continuum plasticity. The incremental load-displacement relationship is derived based on the elastic-plastic stiffness tensor including the elastic stiffness tensor, the plastic modulus, a function representing the yield criterion and a hardening rule, and function representing the plastic potential. The plastic properties are determined from experimental results obtained from testing actual connections. Load-displacement curves for shear walls are calculated using the shear connector model and they are compared with experimental and other computational results. Also, the ultimate horizontal load-carrying capacity is compared to results obtained by an analytical plastic design method. Good agreements are found.

关键词： shear walls     wall diaphragms     finite element modelling     plastic shear connector     analytical modelling     experimental comparison    

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The ITZ microstructure, thickness, porosity and its relation with compressive and flexural strength of

《结构与土木工程前沿（英文）》 2022年 第16卷 第2期   页码 191-201 doi: 10.1007/s11709-021-0792-y

摘要： A new insight into the interfacial transition zone (ITZ) in cement mortar specimens (CMSs) that is influenced by cement fineness is reported. The importance of cement fineness in ITZ characterizations such as morphology and thickness is elucidated by backscattered electron images and by consequences to the compressive (Fc) and flexural strength (Ff), and porosity at various water/cement ratios. The findings indicate that by increasing the cement fineness the calcium silicate hydrate formation in the ITZ is favored and that this can refine the pore structures and create a denser and more homogeneous microstructure. By increasing cement fineness by about 25% of, the ITZ thickness of CMSs was reduced by about 30% and Fc was increased by 7%–52% and Ff by 19%–40%. These findings illustrate that the influence of ITZ features on the mechanical strength of CMSs is mostly related to the cement fineness and ITZ microstructure.

关键词： cement fineness     interfacial transition zone     compressive and flexural strength    

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标题 作者 时间 类型 操作

Dynamic analyses of steel-reinforced super high-strength concrete columns

JIA Jinqing, JIANG Rui, XU Shilang, HOU Tong

期刊论文

Uncertainty of concrete strength in shear and flexural behavior of beams using lattice modeling

期刊论文

Enhanced empirical models for predicting the drift capacity of less ductile RC columns with flexural,shear or axial failure modes

Mohammad Reza AZADI KAKAVAND, Reza ALLAHVIRDIZADEH

期刊论文

Flexural and longitudinal shear performance of precast lightweight steel–ultra-high performance concrete

期刊论文

Shear-flexural strength mechanical model for the design and assessment of reinforced concrete beams subjected

Antonio MARÍ,Antoni CLADERA,Jesús BAIRÁN,Eva OLLER,Carlos RIBAS

期刊论文

Strengthening of reinforced concrete beams using fiber-reinforced cementitious matrix systems fabricated with custom-designed mortar and fabrics

期刊论文

Mechanical properties characterization of different types of masonry infill walls

André FURTADO, Hugo RODRIGUES, António ARÊDE, Humberto VARUM

期刊论文

Structural performance of a façade precast concrete sandwich panel enabled by a bar-type basalt fiber-reinforced polymer connector

期刊论文

Hybrid flexural components: Testing pre-stressed steel and GFRP bars together as reinforcement for flexural

Mohammed FARUQI, Oved I. MATA, Francisco AGUINIGA

期刊论文

Analysis of stiffness and flexural strength of a reinforced concrete beam using an invented reinforcement

Nazim Abdul NARIMAN, Martin HUSEK, Ilham Ibrahim MOHAMMAD, Kaywan Othman AHMED, Diyako DILSHAD, Ibrahim KHIDR

期刊论文

Effect of size on biaxial flexural strength for cement-based materials by using a triangular plate method

Hakan T TURKER

期刊论文

An experimental study on the flexural behavior of heavily steel reinforced beams with high-strength concrete

Yasser SHARIFI, Ali Akbar MAGHSOUDI

期刊论文

Effect of bond enhancement using carbon nanotubes on flexural behavior of RC beams strengthened with

期刊论文

Modeling of shear walls using finite shear connector elements based on continuum plasticity

Ulf Arne GIRHAMMAR, Per Johan GUSTAFSSON, Bo KÄLLSNER

期刊论文

The ITZ microstructure, thickness, porosity and its relation with compressive and flexural strength of

期刊论文