Flexure Members Research Articles

Flexural behavior of LVL made from Australian radiata pine

As a commonly used engineering wood in modern timber constructions, laminated veneer lumber (LVL), produced from small-diameter wood, short-dimension wood, or fast-growing wood, significantly enhances material properties to meet the mechanical and physical requirements in structural engineering. This study aims to investigate the feasibility of utilizing fast-growing Australian radiata pine to produce structural LVL, providing essential theoretical support for its application in civil engineering. The investigation focuses specifically on Australian radiata pine LVL (RP-LVL) and involves a systematic experimental study to assess the bending performance of RP-LVL under various bending directions and specimen sizes. The findings reveal that the edgewise bending strength of RP-LVL is comparatively lower than its flatwise bending strength. Nevertheless, RP-LVL exhibits superior bending strength compared to conventional glulam and dimensional lumber, rendering it an attractive and suitable building material for achieving enhanced bending performance in flexure members. Moreover, the study identifies significant influences of height and width on the bending strength of RP-LVL. Consequently, prediction method is proposed to calculate the bending strength of RP-LVL, considering these size influences. Importantly, the size influences on bending strength are quantified to provide a comprehensive evaluation of the bending capacity of RP-LVL flexure members.

Seismic Design and Performance of Composite Coupling Beam-to-SpeedCore Wall Connections

Coupled composite plate shear walls—concrete filled (CC-PSW/CFs) are an effective seismic lateral-force-resisting system for the design and construction of mid- to high-rise buildings around the world. The coupled system consists of two or more composite plate shear walls—concrete filled (C-PSW/CFs) connected to each other using composite coupling beams located at the story heights. The CC-PSW/CF system can provide higher overturning moment capacity, lateral stiffness, and ductility than uncoupled walls. Concrete-filled steel box sections are typically used for the composite coupling beams, which are designed to be flexure critical members. When the CC-PSW/CF system is subjected to lateral seismic forces, plastic hinge formation and inelastic deformations (energy dissipation) occur near the ends of most of coupling beams along the structure’s height, followed by flexural hinging of the C-PSW/CFs, typically at the base. This paper presents the details and design of four composite coupling beam-to-C-PSW/CF connection configurations. Six connection specimens representing the four connection configurations, with beam clear span-to-section depth, Lb/d, ratios of 3.5 and 5.1, were designed and tested. The lateral force-displacement and moment-rotation responses of the specimens are summarized. All six composite coupling beam-to-C-PSW/CF wall connection specimens (1) developed and exceeded the plastic flexural capacities, Mp, of the coupling beams calculated using the plastic stress distribution method and (2) developed chord rotation capacities greater than 0.03 radian before their flexural strength degraded to 80% of the plastic moment capacity, Mp.

An Experimental Study to Mitigate Environmental Impacts by Transforming Waste Plastic Bags into Paving Blocks and Roof Tiles

The world’s plastic bag problem adversely impacts the environment daily. Plastic bags decompose after years, and some may take centuries, leading to pollution. Society relies on plastic bags for every task, which causes many problems for humans and aquatic life. Focusing on Sustainable Development Goal 12 (SDG 12), this research used waste plastic bags melted in a boilery to develop plastocrete to cast plastocrete paving blocks and roofing tiles. Compressive and split tensile strength tests were performed on plastocrete paving blocks, while a thermal insulation test was performed on roofing tiles in the Concrete Lab of our Department. The compressive strength test on plastocrete showed that it can easily replace concrete pavement blocks after giving good compressive strengths compared with concrete blocks. Being very low in tensile strength, plastocrete is not recommended for flexure members. The thermal insulation test results indicate that using plastic bags as roofing tiles decreases thermal conductivity compared with a controlled reinforced slab. Hence, it is concluded that plastocrete will help reduce pollution in the terrestrial and aquatic environment and can be an effective waste disposal solution. The plastocrete-led paving blocks and roofing tiles not only help economically but also help preserve nature and the environment from land pollution.

Blast retrofit of one-way reinforced concrete members using externally bonded FRP and FRP anchorage

This paper presents the results of nine as-built and carbon fiber reinforced polymer (CFRP) retrofitted reinforced concrete panels subjected to simulated blast loading using a pneumatically operated shock tube. The objective of the study was to characterize the blast response of CFRP retrofitted reinforced concrete panels, with and without supplemental mechanical anchorage applied to the CFRP. The results indicate that retrofitting can significantly increase the strength and stiffness of reinforced concrete flexure members and greatly enhance the displacement time-history response over non-retrofitted members. Debonding of the externally bonded CFRP was the failure mode for all retrofitted members. FRP anchors, designed to prevent or delay debonding failures through mechanical end-anchorage, were found to substantially enhance the performance of panels experiencing critical diagonal crack debonding. However, the FRP anchors were found to have no substantial effect on retrofit performance for the case plate-end interfacial debonding failures. In addition, the displacement time-histories for as-built and FRP retrofitted panel obtained through detail single degree of freedom analysis were found correlate well with those obtained experimentally. Finally, a discussion on the practical considerations of using externally bonded FRP retrofits to resist blast loads and recommendations for protective design are presented.

Contribution of higher modes in the dynamic response of reinforced concrete member subjected to blast

Response of reinforced concrete structures subjected to blast load of high intensity and short duration is difficult to analyze. P-I (pressure-impulse) curves are one of the approaches for describing structural response against blast load. Design codes also suggest preparing P-I curves based on SDOF for obtaining structural response subjected to blast. Blast load excites higher modes of vibrations. The SDOF analysis does not cover the higher modes effect.The structural dynamic response of RC flexure members under a varying range of explosion scenarios was predicted by carrying out investigations. The linear elastic beam with variable boundary conditions was analyzed using the Modal superposition method based upon Euler-Bernoulli, Rayleigh, Shear, and Timoshenko theories. For various ranges of the blast, Iso-damage (P-I) curves, including the effect of higher modes, were generated, and the types of failure were established. These iso-damage curves differ significantly from those obtained using the SDOF concept for the case of blast in the dynamic and impulsive regime. In the case of near blast, understandably higher modes (both flexure and shear) play a significant role. The present study suggests that the Timoshenko formulation yields an accurate response irrespective of the Flexibility of the structure.

Experimental study on flexural behavior of light steel hollow flange beam with various stiffening arrangements

Nowadays, cold-form steel section is widely used in the construction of steel structure as they proved more efficient as compared to the hot-rolled section. The steel beams are also called as bending or flexure members and are susceptible to lateral torsional as well as distortion buckling, which ultimately leads to reduction in moment of resistance of the sections. To conquer this light steel beam (LSB) is developed. Observation on failure pattern of light steel beam from the previous research shows that it becomes essential to strengthen the flexural members. Therefore, in this study an attempt has been made to study the effectiveness of various strengthening alternatives of the LSB, i.e., the section with and without notch and provision of stiffeners at web and flange. As a result, flexural strength, failure pattern and deflection parameters have been studied. To validate the failure patterns and deflection, the beam specimens were analyzed using ANSYS v 12. The experimental and finite element results reveal that there is an increased in bending strength of 25.6% when the stiffener is provided on web as compared to the other stiffening arrangements. For that reason, an intermediate web stiffening arrangement is found to be better than the intermediate flange sections.

Comparative post-yield performance evaluation of flexure member with corroded reinforcement

Existing plastic hinge models for reinforced concrete beams do not consider the effect of reinforcement corrosion. This paper represents the plastic hinge model of corroded Reinforced Concrete (RC) beams tested experimentally as well as investigated analytically through nonlinear finite element modeling. An attempt is then made to arrive at simple empirical equation for maximum moment including the percentage of corrosion, using soft computing technique of Genetic Programming (GP). Simply supported beams are analysed with varying grades of concrete and type of reinforcement along with the condition of reinforcement by applying two-point loading (approximately 1/3rd and 2/3rd of span) and verified with the experiments performed. Test results show that the model can accurately predict the force deflection response and failure mode. The results show decrease in the moment and rotation capacity with the increase in corrosion percentage of reinforcement bars used in RC beams. The equation obtained as an output of GP models indicates the influence of yield strength of reinforcement, concrete grade and percentage of corrosion of RC beam over maximum moment carrying capacity.

FE modeling of concrete beams and columns reinforced with FRP composites

Compression and flexure members such as columns and beams are critical in a structure as its failure could lead to the collapse of the structure. In the present work, numerical analysis of square and circle short columns, and reinforced concrete (RC) beams reinforced with fiber reinforced polymer composites are carried out. This work is divided into two parts. In the first part, numerical study of axial behavior of square and circular concrete columns reinforced with Glass Fiber Reinforced Polymer (GFRP) and Basalt Fiber Reinforced Polymer (BFRP)bars and spiral, and Carbon Fiber Reinforced Polymer (CFRP) wraps is conducted. The results of the first part showed that the axial capacity of the circular RC columns reinforced with GFRP increases with the increase of the longitudinal reinforcement ratio. In addition, the results of the numerical analysis showed good correlation with the experimental ones. An interaction diagram for BFRP RC columns is also developed with considering various eccentricities. The results of numerical modeling of RC columns strengthened with CFRP wraps revealed that the number and the spacing between the CFRP wraps provide different levels of ductility enhancement to the column. For the cases considered in this study, column with two middle closely spaced CFRP wraps demonstrated the best performance. In the second part of this research, flexural behavior of RC beams reinforced with BFRP, GFRP and CFRP bars is investigated along with validation of the numerical model with the experimental tests. The results resembled the experimental observations that indicate significant effect of the FRP bar diameter and type ont he flexural capacity of the RC beams. It was also shown that Increasing the number of bars while keeping the same reinforcement ratio enhanced the stiffness of the RC beam.

Numerical modeling for damaged reinforced concrete slab strengthened by ultra-high performance concrete (UHPC) layer

Ultra-high performance concrete (UHPC) has been developed as an innovative cementitious based material. It can be used for repairing and strengthening existing reinforced concrete (RC) structures because of its excellent mechanical performance, such as high tensile and compressive strengths, long-term durability, and low permeability. However, when using UHPC to strengthen existing RC structures for flexure members, there is limited information on simulating existed cracks in RC structures and considering interface modeling between RC substrate and UHPC overlay. This research developed a finite element (FE) model to investigate flexural behaviors of UHPC-RC composite slab with introducing existed cracks in RC substrate by geometry discontinuous, approximately matched with experimental results previously published by the authors. Meanwhile, based on recent research on the bond strength of UHPC to concrete, a UHPC-RC interfacial model was included in the FE model. The FE model was validated with experimental laboratory results previously published by the authors, and a good agreement was obtained between numerical and experimental results. Finally, a parameter study was conducted to investigate the strengthening effects and optimizing strengthening parameters by using the developed FE model. Results showed that the effect of existing cracks on the ultimate flexure capacity of UHPC-RC cannot be neglected, and the interface model has a precise accuracy in FE modeling.

Non-Smooth Behavior of Reinforced Concrete Beam Using Extended Finite Element Method

Flexure members such as reinforced concrete (RC) simply supported beams subjected to two-point loading were analyzed numerically. The Extended Finite Element Method (XFEM) was employed for the treatment the non-smooth h behaviour such as discontinuities and singularities. This method is a powerful technique used for the analysis of the fracture process and crack propagation in concrete. Concrete is a heterogeneous material that consists of coarse aggregate, cement mortar and air voids distributed in the cement paste. Numerical modeling of concrete comprises a two-scale model, using mesoscale and macroscale numerical models. The effectiveness and validity of the Meso-Scale Approach (MSA) in modeling of the reinforced concrete beams with minimum reinforcement was studied. ABAQUS program was utilized for Finite Element (FE) modeling and analysis of the beams. On the other hand, mesoscale modeling of concrete constituents was executed with the aid of ABAQUS PYTHON language and programing using excel sheets. The concrete beams under flexure were experimentally investigated as well as by the numerical analysis. The comparison between experimental and numerical results showed that the mesoscale model gives a better indication for representing the concrete models in the numerical approach and a more appropriate result when compared with the experimental results.

Design and Analysis of Multistory Building by using Shearwall Technology

In early 20th century there is a revolutionary change in software development and programing that change also helped the field of civil and structural engineering to make the analysis made easy by developing easy user interface software’s. By the development of those sophisticated structural design software’s even the G+10 building can analyze and design within 48 hours of time. But if the same building, if we design by manual calculations it takes lot of time and the design report is like a book with thousands of pages. In this particular thesis the G+5 residential building is designed by adopting structural wall systems without any columns. The analysis and design of super structure done in Etabs software for dead load, live load, earthquake, wind load. The uncracked model is prepared and checked against the lateral deflections due to lateral forces and vertical deflections of elements due to self-weight and modal analysis is carried out. The modal analysis is carried based on tall story code and earth quake codes, the translation modes and rotation modes are observed Cleary and designed the structure against the torsional buckling also. The same structure is also analyzed and designed for serviceability criteria’s and strength criteria’s by adopting the modification factors to achieve the accurate values about the long term deflection in both vertical and horizontal direction. The auto construction sequence method adopted for the finding the long term creep deflection values of the flexure members. All the members are designed against all kind of static and dynamic loads. By adopting the geotechnical report of the soil, the foundation system is adopted based on the S.B.C value and the allowable settlement value and the shear stress and settlement and soil pressure values are checked. The design of the entire footing system along with soil structure interaction is done in SAFE software and the detailing and design of the elements are done by taking one element in each type in drafting software.

A torsional sub-milli-Newton thrust balance based on a spring leaf strain gauge sensor.

The development of a torsional thrust balance with a spring leaf sensor based on strain gauges is described in the present work. The balance is capable of measuring thrust forces up to 225 mN with micro-Newton resolution. Steady state thrust force is hereby measured via displacement of the balance arm, which in return leads to a displacement of the sensor. The strain induced by the force on the flexure member of the sensor is measured using strain gauges. The development of the sensor and the dynamic behavior of the balance are based on analytical analysis. The oscillatory motion of the balance arm is damped by a passive eddy current damper. An automated calibration mechanism with a pulley and calibration weights is used to calibrate the balance prior to measurement. Atmospheric as well as in situ calibration, single and multiple calibration runs with automatic averaging of calibration coefficients, is possible at all operational stages. The calibration of the balance exhibits excellent linearity and repeatability, while the dynamic behavior shows some deviations from the analytical prediction. The sensor exhibits low noise, with an estimated resolution within 15 μN. A state-of-the-art ratio of resolution to measurement range is achieved. As a conclusion, a series of thrust measurements in the range of 29 μN-37.04 mN are presented and briefly discussed.

Non-linear Analysis Reinforced Concrete Flexure Members Using Elements with Axial – Shear Coupling

This paper explains the formulation of Applied Element Method (AEM) as applied to plain and reinforced concrete beams as two-dimensional structures by primarily implementing material non-linearity. Both concrete and steel reinforcement have non-linear stress-strain curve in the model. A multi linear curve is assumed for reinforcement and concrete is modeled as a progressively fracturing solid. Static linear analysis of a reinforced beam using this method was compared with finite element and coupled boundary element method solutions. Static non-linear analysis of plain concrete beam using this method was compared with results of fracture mechanics model and published experimental results. The results were in good agreement with established analysis methods and experimental data. Advantages of AEM which is simple and straightforward in the modeling of reinforced concrete members are also discussed.

Analytical Compliance Modeling of Serial Flexure-Based Compliant Mechanism Under Arbitrary Applied Load

Analytical compliance model is vital to the flexure- based compliant mechanism in its mechanical design and motion control. The matrix is a common and effective approach in the compliance modeling while it is not well developed for the closed-loop serial and parallel compliant mechanisms and is not applicable to the situation when the external loads are applied on the flexure members. Concise and explicit analytical compliance models of the serial flexure-based compliant mechanisms under arbitrary loads are derived by using the matrix method. An equivalent method is proposed to deal with the situation when the external loads are applied on the flexure members. The external loads are transformed to concentrated forces applied on the rigid links, which satisfy the equations of static equilibrium and also guarantee that the deformations at the displacement output point remain unchanged. Then the matrix method can be still adopted for the compliance analysis of the compliant mechanism. Finally, several specific examples and an experimental test are given to verify the effectiveness of the compliance models and the force equivalent method. The research enriches the matrix method and provides concise analytical compliance models for the serial compliant mechanism.

Compliance modeling of planar flexure-based mechanisms and its application to micro-motion stages

This article presents the compliance modeling method of flexure-based mechanisms. The relationship between deformations and loads of the flexure members and the end effector is analyzed according to the zero virtual work principle. Using the matrix method, concise compliance equations for flexure serial and parallel structures are derived in conjunction with consideration of the compliance calculation errors of flexure hinges. Finally, relationships between the output compliances and geometrical parameters of a 3-revolute-revolute-revolute micro-motion stage are discussed. To validate the proposed compliance modeling method, the output compliances calculated by the empirical and theoretical compliance equations are subsequently compared with values derived from finite element analysis (FEA). The comparisons indicate that the results obtained from the empirical compliance equations are in good agreement with those derived from FEA, whereas the errors calculated by the theoretical equations are much larger, which demonstrate the accuracy of the empirical compliance equations and validate the proposed compliance modeling method.

지간-높이 비에 따른 스트럿-타이 모델과 ACI 고전적인 방법의 설계 비교

깊은 보는 지간-높이 비가 중요한 파라미터이다. 깊은 보를 설계할 때, ACI 318-02 이후 버전에서는 응력의 비선형 분포로 인해서 고전적인 설계 방법이 아니라 스트럿-타이 모델을 부록에 수록하여, 이 방법으로 설계하도록 하고 있다. 본 연구에서는 ACI 고전적인 설계방법과 스트럿-타이 모델을 비교, 분석하였다. 파라미터 연구로 지간-높이 비를 변화시켰으며, 총 68개의 샘플을 분석하였다. 결과로 고전적인 설계 방법과 스트럿-타이 모델은 빔의 지간-높이 비에 따라서 각각 장단점이 있으며, 본 논문에 깊은 보를 설계할 때의 팁이 제시되어 있다. Since clear span-to-depth ratio is used to define what is so called a deep beam, it is an important parameter ratio for study about deep beam. Deep beams can be designed by flexure design method, and shear provided by concrete (<TEX>$v_c$</TEX>) and by steel (<TEX>$v_s$</TEX>) for deep flexure members are provided in ACI 318-99 [1]. But in later version of ACI (from ACI 318-02) it is not provided and deep beams shall be designed either by taking into account nonlinear distribution of strain or by Appendix A of Strut-and-Tie Models (STM). The trend of deep beam design seems to be familiar with strut-and-tie model, but ACI traditional design is not forgotten. By comparing these two method, there should a point which definitely explain the different between the two methods. In this study, 68 samples result of steel, after reinforcement arrangement, are taken to be analyzed.

A study of factors affecting the flexural tensile strength of concrete

The deflection and cracking behavior of concrete structure depend on the flexural tensile strength of concrete. Many factors have been shown to influence the flexural tensile strength of concrete, particularly the level of stress, size, age and confinement to concrete flexure member, etc. The concrete members, in general, are of large continuous size and have at least minimum reinforcement introducing a confining effect to the concrete. The confining reinforcement increases ductility and large deflections in structures provide a good warning of failure prior to complete failure of the flexure member and also for efficient use of constructional material, it is desirable to take full advantage of long-term strength gain. Therefore, the effect of the factors like level of stress, age and confinement of concrete member should be given prime importance while studying the flexure tensile strength of concrete. This paper presents an experimental study done to predict the flexural tensile strength considering the confinement conditions and age of concrete for a wide range of concrete strengths (from 30 to 85MPa). It is concluded that the factors like confinement conditions and age of concrete should be given due consideration in deriving the flexural tensile strength and compressive strength proportionality equations.

Analytical and experimental investigation for bond behaviour of newly developed polystyrene foam particles’ lightweight concrete

Structural lightweight concrete (LWC) is of high importance to the construction industry, as it is cost effective and highly advantageous. A new kind of LWC was produced at the Department of Structural Engineering of Ain Shams University in 2005, which combines the advantages of normal density concrete, cellular concrete and high workability concrete through partially replacing the normal weight aggregates with polystyrene foam particles. This leads to concrete’s unit weight reduction while maintaining adequate strength. The latter material can therefore be produced using standard methods familiar to the construction industry with a dry unit weight of 18.50kN/m3, which in turn leads to self weight reduction of 15–20% and the associated decrease in the structure’s overall cost, hence, providing a feasible challenge to normal weight concrete (NWC). The bond behaviour of structural polystyrene foam lightweight concrete (PF-LWC) was investigated analytically and experimentally. The experimental program incorporated two phases. The first phase was performed on the standard pull-out specimens to compare its results with the commonly conducted bond testing and to abstract the bond slip curve of the standard pull-out test specimens. The second phase deal with a deduced beam-end specimen to assess the behaviour of bond between reinforcing bars and concrete in flexure members. Then analytical investigation of the obtained experimental results was performed to develop a model capable of assessing the structural bond behaviour of PF-LWC flexural members. The defining parameters of the bond stress–slip curve were modified for NWC and PF-LWC using the best fit technique to the experimental results in order to add the bar diameter as a variable in the bond stress–slip relationship. The defining parameters of the CEB-FIP 1990 bond stress–slip curve [1] were modified for NWC and PF-LWC using the best fitting technique.

Bond-slip parameter determination procedure of RC flexure member strengthened with prestressed CFRP plates

The purpose of this study is to evaluate the flexural behavior of RC (Reinforced Concrete) beams strengthened with prestressed CFRP (Carbon Fiber Reinforced Polymers) plates and suggest the prediction method for the strength of RC flexure member strengthened with prestressed CFRP plate by bond-slip parameter determination procedure for retrofit design. The uniaxial tensile test of CFRP plate specimen and the pull-test of CFRP plate bonded to concrete are carried out to investigate the strengthening effect of CFRP plate on RC members in detail. The behavior model of CFRP plate and the bond-slip model to be implemented in finite element analysis are proposed based on a parametric study and test results. The proposed method of flexural strength prediction for RC beams strengthened with prestressed CFRP plates are verified through comparing and analyzing with experimental results of this study. Through verifications, it is determined that the proposed strength prediction method can effectively be applied in flexural retrofit design of RC beams using prestressed CFRP plates.

The Study on Bond and Anchorage Behavior of RC Flexural Members with Inorganic Adhesive Powder

To study the anchorage performance of the inorganic post-installed RC flexural members in flexural test, this paper simulates the stress state of the inorganic post-installed RC flexural members in practical projects. Through cyclic loading test, the anchorage performance of the inorganic post-installed RC flexural members in the bending tensile conditions is checked. This paper studies the anchorage performance of the post-installed steel at the state of bending tension, such as: adhesion stress, bond-slip relationship, the load carrying capacity, deformation behavior of the flexural member, and compare with those of normal member. The result indicates that with anchorage length of 20D in flexure member, the load carrying capacity of the inorganic post-installed reinforced concrete is apparently worse to those of normal members under repeated loading test; In case that anchorage length is invariable, load carrying capacity can be significantly enhanced through improving the concrete strength level. The anchorage zone is easily damaged, and the steel is easily slipped, which result in the decrease of the load carrying capacity, so some measures must be taken if inorganic adhesive powder is used in practical projects.