Search results for: reinforced concrete arched structure

Authors: Ceyhun Aksoylu, Rifat Sezer

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In this study, a strengthening method applicable without any evacuation process was investigated. In this analytical study, the pushover analysis results carry out by using the software of SAP2000. For this purpose, 1/3 scaled, 1-bay and 2-story R/C seven frames having usual deficiencies faults produced, one of which were not strengthened, but having brick-infill wall and the other 3 frames with infill walls strengthened with various shaped of high strength-precast diagonal concrete panels. The prepared analytical models investigated under reversed-cyclic loading that resembles the seismic effect. As a result of the analytical study, the properties of the reinforced concrete frames, such as strength, rigidity, energy dissipation capacity, etc. were determined and the strengthened models were compared with the unstrengthened one having the same properties. As a result of this study, the contributions of precast diagonal concrete applied on the infill walls of the existing frame systems against seismic effects were introduced with its advantages and disadvantages.

Keywords: RC frame, seismic effect, infill wall, strengthening, precast diagonal concrete panel, pushover analysis

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Authors: H. S. Youm, S. G. Hong

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This paper presents the test results on 5 slab-column connection specimens with Ultra High Performance Fiber-Reinforced Concrete (UHPFRC) overlay including 1 control specimen to investigate retrofitting effect of UHPFRC overlay on the punching shear capacity. The test parameters were the thickness of the UHPFRC overlay and the amount of steel re-bars in it. All specimens failed in punching shear mode with abrupt failure aspect. The test results showed that by adding a thin layer of UHPFRC over the Reinforced Concrete (RC) substrates, considerable increases in global punching shear resistance up to 82% and structural rigidity were achieved. Furthermore, based on the cracking patterns the composite systems appeared to be governed by two failure modes: 1) diagonal shear failure in RC section and 2) debonding failure at the interface.

Keywords: punching shear strength, retrofit, slab-column connection, UHPFRC, UHPFRC overlay

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Authors: HoYoung Son, Ki Young Kim, Woo Young Jung

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This study investigated the change of weir structure performances when durability of concrete, which is the main material of weir structure, decreased due to their aging by mean of seismic fragility analysis. In the analysis, it was assumed that the elastic modulus of concrete was reduced by 10% in order to account for their aged deterioration. Additionally, the analysis of seismic fragility was based on Monte Carlo Simulation method combined with a 2D nonlinear finite element in ABAQUS platform with the consideration of deterioration of concrete. Finally, the comparison of seismic fragility of model pre- and post-deterioration was made to study the performance of weir. Results show that the probability of failure in moderate damage for deteriorated model was found to be larger than pre-deterioration model when peak ground acceleration (PGA) passed 0.4 g.

Keywords: weir, FEM, concrete, fragility, aging

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Authors: Serikma Mourad, Mezidi Amar

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The conception (design) of an earthquake-resistant structure is a complex problem seen the necessity of meeting the requirements of security been imperative by the regulations, and of economy been imperative by the increasing costs of the structures. The resistance of a building in the horizontal actions (shares) is mainly ensured by a mixed brace system; for a concrete building, this system is constituted by frame or shells; or both at the same time. After the earthquake of Boumerdes (May 23; 2003) in Algeria, the studies made by experts, ended in modifications of the Algerian Earthquake-resistant Regulation (AER 99). One of these modifications was to widen the use of shells for the brace system. This modification has create a conflict on the quantities, the positions and the type of the shells at adopt. In the present project, we suggest seeing the effect of the variation of the dimensions, the localization and the conditions of rigidity in extremities of shells. The study will be led on a building (F+5) implanted in zone of seismicity average. To do it, we shall proceed to a classic dynamic study of a structure by using 4 alternatives for shells by varying the lengths and number in order to compare the cost of the structure for 4 dispositions of the shells with a technical-economic study of the brace system by the use of different dispositions of shells and to estimate the quantities of necessary materials (concrete and steel).

Keywords: reinforced concrete, mixed brace system, dynamic analysis, beams, shells

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Authors: Chrysanthos Maraveas, Argiris Plesias, Garyfalia G. Triantafyllou, Konstantinos Petronikolos

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The current paper presents a structural assessment and proposals for retrofit of the National Youth Foundation Building, an existing reinforced concrete (RC) building in the city of Igoumenitsa, Greece. The building is scheduled to be renovated in order to create a Municipal Cultural Center. The bearing capacity and structural integrity have been investigated in relation to the provisions and requirements of the Greek Retrofitting Code (KAN.EPE.) and European Standards (Eurocodes). The capacity of the existing concrete structure that makes up the two central buildings in the complex (buildings II and IV) has been evaluated both in its present form and after including several proposed architectural interventions. The structural system consists of spatial frames of columns and beams that have been simulated using beam elements. Some RC elements of the buildings have been strengthened in the past by means of concrete jacketing and have had cracks sealed with epoxy injections. Static-nonlinear analysis (Pushover) has been used to assess the seismic performance of the two structures with regard to performance level B1 from KAN.EPE. Retrofitting scenarios are proposed for the two buildings, including type Λ steel bracings and placement of concrete shear walls in the transverse direction in order to achieve the design-specification deformation in each applicable situation, improve the seismic performance, and reduce the number of interventions required.

Keywords: earthquake resistance, pushover analysis, reinforced concrete, retrofit, strengthening

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Authors: Ju-Young Hwang, Hyo-Gyoung Kwak

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This paper introduces a numerical analysis method for reinforced-concrete (RC) structures exposed to fire and compares the result with experimental results. The proposed analysis method for RC structure under the high temperature consists of two procedures. First step is to decide the temperature distribution across the section through the heat transfer analysis by using the time-temperature curve. After determination of the temperature distribution, the nonlinear analysis is followed. By considering material and geometrical nonlinearity with the temperature distribution, nonlinear analysis predicts the behavior of RC structure under the fire by the exposed time. The proposed method is validated by the comparison with the experimental results. Finally, prediction model to describe the status of after-cooling concrete can also be introduced based on the results of additional experiment. The product of this study is expected to be embedded for smart structure monitoring system against fire in u-City.

Keywords: RC, high temperature, after-cooling analysis, nonlinear analysis

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Authors: Seyed Amin Vakili, Sahar Sadat Vakili, Seyed Ehsan Vakili, Nader Abdoli Yazdi

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The aim of this paper is to examine the behavior of elastic stability of reinforced and composite concrete struts with axial loads. The objective of this study is to verify the ability of the Modified Newmark Method to include geometric non-linearity in addition to non-linearity due to cracking, and also to show the advantage of the established method to reconsider an ignored minor parameter in mathematical modeling, such as the effect of the cracking by extra geometric bending moment Ny on cross-section properties. The purpose of this investigation is not to present some new results for the instability of reinforced or composite concrete columns. Therefore, no kinds of non-linearity involved in the problem are considered here. Only as mentioned, it is a part of the verification of the new established method to solve two kinds of non-linearity P- δ effect and cracking together simultaneously. However, the Modified Newmark Method can be used to solve non-linearity of materials and time-dependent behavior of concrete. However, since it is out of the scope of this article, it is not considered.

Keywords: stability, buckling, modified newmark method, reinforced

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Authors: Mohammed Almograbi

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Libya is one of the largest producers of dates from date palm, generating about 60000 tonnes of date palm seeds (DPS) annually. This large amount of seeds led to studies into the possible use as aggregates in lightweight concrete for some special structures. The utilization of DPS as aggregate in concrete provides a good solution as alternative aggregate to the stone aggregate. It has been recognized that, DPS can be used as coarse aggregate in structural lightweight concrete industry. For any structure member, the durability is one of the most important considerations during its service life. This paper presents the durability properties of DPS concrete. These include the water permeability, water absorption, sorptivity and chloride penetration. The test results obtained were comparable to the conventional lightweight concrete.

Keywords: date palm seeds, lightweight concrete, durability, sustainability, permeability of concrete, water absorption of concrete, sorptivity of concrete

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Authors: Palak J. Shukla, Atul K. Desai, Chentankumar D. Modhera

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For any country in the world, it has become a priority to protect the critical infrastructure from looming risks of terrorism. In any infrastructure system, the structural elements like lower floors, exterior columns, walls etc. are key elements which are the most susceptible to damage due to blast load. The present study revisits the state of art review of the design and analysis of reinforced concrete panels subjected to blast loading. Various aspects in association with blast loading on structure, i.e. estimation of blast load, experimental works carried out previously, the numerical simulation tools, various material models, etc. are considered for exploring the current practices adopted worldwide. Discussion on various parametric studies to investigate the effect of reinforcement ratios, thickness of slab, different charge weight and standoff distance is also made. It was observed that for the simulation of blast load, CONWEP blast function or equivalent numerical equations were successfully employed by many researchers. The study of literature indicates that the researches were carried out using experimental works and numerical simulation using well known generalized finite element methods, i.e. LS-DYNA, ABAQUS, AUTODYN. Many researchers recommended to use concrete damage model to represent concrete and plastic kinematic material model to represent steel under action of blast loads for most of the numerical simulations. Most of the studies reveal that the increase reinforcement ratio, thickness of slab, standoff distance was resulted in better blast resistance performance of reinforced concrete panel. The study summarizes the various research results and appends the present state of knowledge for the structures exposed to blast loading.

Keywords: blast phenomenon, experimental methods, material models, numerical methods

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Authors: Younghoo Choi, Yong Jun, Jinkoo Kim

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In this study seismic performance of typical reinforced concrete staggered wall system structures was evaluated through nonlinear static and incremental dynamic analyses. To this end, and 15-story SWS structures were designed and were analyzed to obtain their nonlinear force-displacement relationships. The analysis results showed that the 5-story SWS structures failed due to yielding of columns and walls located in the lower stories, whereas in the 15-story structures plastic hinges were more widely distributed throughout the stories.

Keywords: staggered wall systems, reinforced concrete, seismic performance

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Authors: Sultan Daud, John P. Forth, Nikolaos Nikitas

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The current study aims to highlight the loading characteristics impact on the time evolution (focusing particularly on long term effects) of the deformation of realized reinforced concrete beams. Namely the tension stiffening code provisions (i.e. within Eurocode 2) are reviewed with a clear intention to reassess their operational value and predicting capacity. In what follows the experimental programme adopted along with some preliminary findings and numerical modelling attempts are presented. For a range of long slender reinforced concrete simply supported beams (4200 mm) constant static sustained and repeated cyclic loadings were applied mapping the time evolution of deformation. All experiments were carried out at the Heavy Structures Lab of the University of Leeds. During tests the mid-span deflection, creep coefficient and shrinkage strains were monitored for duration of 90 days. The obtained results are set against the values predicted by Eurocode 2 and the tools within an FE commercial package (i.e. Midas FEA) to yield that existing knowledge and practise is at times over-conservative.

Keywords: Eurocode2, midas fea, repeated, sustained loading.

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Authors: Mina Iskander, Mina Melad, Mourad Yasser, Waleed Abdel Rahim, Amr Mosa, Mohamed El Lahamy, Ezzeldin Sayed-Ahmed, Mohamed Abou-Zeid

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Strengthening of reinforced concrete beams in flexure using externally bonded composite laminate of high tensile strength is easy and of the minimum cost compared to traditional methods such as increasing the concrete section depth or reinforcement that requires formwork and curing which affect the structure usability. One of the main limitations of this technique is debonding of the externally bonded laminate, either by end delamination or by mid-span flexural crack-induced debonding. ACI 440.2-08 suggests that using side-bonded FRP laminate in the flexural strengthening of RC beams may serve to limit the extent and width of flexural cracks. Consequently, this technique may decrease the effect of flexural cracks on initiating the mid-span debonding; i.e. delays the flexural crack-induced debonding. Furthermore, bonding the FRP strips to the side of the beam may offer an attractive, practical solution when the soffit of this beam is not accessible. This paper presents an experimental programme designed to investigate the effect of using externally bonded CFRP laminate on the sides of reinforced concrete beams and compares the results to those of bonding the CFRP laminate to the soffit of the beams. In addition, the paper discusses the effect of using end anchorage by U-wrapping the CFRP strips at their end zones with CFRP sheets for beams strengthened with soffit-bonded and side-bonded CFRP strips. Thus, ten rectangular reinforced concrete beams were tested to failure in order to study the effect of changing the location of the externally bonded laminate on the flexural capacity and ductility of the strengthened beams. Pultruded CFRP strips were bonded to the soffit of the beams or their sides to check the possibility of limiting the flexural cracking in mid-span region, which is the main reason for mid-span debonding. Pre-peg CFRP sheets were used near the support as U-wrap for the beam to act as an end-anchorage for the externally bonded strips in order to delay/prevent the end delamination. Strength gains of 38% and 43% were recorded for the soffit-bonded and the side-bonded composite strips with end U-wrapped sheets, respectively. Furthermore, beams with end sheets applied as an end anchorage showed higher ductility than those without these sheets.

Keywords: flexural strengthening, externally bonded CFRP, side-bonded CFRP, CFRP laminates

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Authors: S. Iffat, B. Bose

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Concrete as a construction material is versatile because it displays high degree of fire-resistance. Concrete’s inherent ability to combat one of the most devastating disaster that a structure can endure in its lifetime, can be attributed to its constituent materials which make it inert and have relatively poor thermal conductivity. However, concrete structures must be designed for fire effects. Structural components should be able to withstand dead and live loads without undergoing collapse. The properties of high-strength concrete must be weighed against concerns about its fire resistance and susceptibility to spalling at elevated temperatures. In this paper, the causes, effects and some remedy of deterioration in concrete due to fire hazard will be discussed. Some cost effective solutions to produce a fire resistant concrete will be conversed through this paper.

Keywords: concrete, fire, spalling, temperature, compressive strength, density

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Authors: H. Nikzad, S. Yoshitomi

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In this paper, the optimal seismic design of reinforced concrete shear wall-frame building structures was done using structural optimization. The optimal section sizes were generated through structural optimization based on linear static analysis conforming to American Concrete Institute building design code (ACI 318-14). An analytical procedure was followed to validate the accuracy of the proposed method by comparing stresses on structural members through output files of MATLAB and ETABS. In order to consider the difference of stresses in structural elements by ETABS and MATLAB, and to avoid over-stress members by ETABS, a stress constraint ratio of MATLAB to ETABS was modified and introduced for the most critical load combinations and structural members. Moreover, seismic design of the structure was done following the International Building Code (IBC 2012), American Concrete Institute Building Code (ACI 318-14) and American Society of Civil Engineering (ASCE 7-10) standards. Typical reinforcement requirements for the structural wall, beam and column were discussed and presented using ETABS structural analysis software. The placement and detailing of reinforcement of structural members were also explained and discussed. The outcomes of this study show that the modification of section sizes play a vital role in finding an optimal combination of practical section sizes. In contrast, the optimization problem with size constraints has a higher cost than that of without size constraints. Moreover, the comparison of optimization problem with that of ETABS program shown to be satisfactory and governed ACI 318-14 building design code criteria.

Keywords: structural optimization, seismic design, linear static analysis, etabs, matlab, rc shear wall-frame structures

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Authors: Androniki-Anna Doulgeroglou, Panagiotis Kotronis, Giulio Sciarra, Catherine Bouillon

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The interaction diagrams are functions that define ultimate states expressed in terms of generalized forces (axial force, bending moment and shear force). Two characteristic states for reinforced concrete (RC) sections are proposed: the first characteristic state corresponds to the yield of the reinforcement bars and the second to the peak values of the generalized forces generalized displacements curves. 3D numerical simulations are then conducted for RC columns and the global responses are compared to experimental results. Interaction diagrams for combined flexion, shear and axial force loading conditions are numerically produced for symmetrically RC square sections for different reinforcement ratios. Analytical expressions of the interaction diagrams are also proposed, satisfying the condition of convexity. Comparison with interaction diagrams from the Eurocode is finally presented for the study cases.

Keywords: analytical convex expressions, finite element method, interaction diagrams, reinforced concrete

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Authors: Gautam, Gurcharan Singh, Mandeep Kaur, Yogesh Aggarwal, Sanjeev Naval

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The present ground reality scenario of suffering of humanity shows the evidence of failure to take wrong decisions to shape the civilization with Irresponsibilities in the history. A strong positive will of right responsibilities make the right civilization structure which affects itself and the whole world. Present suffering of humanity shows and reflect the failure of past decisions taken to shape the true culture with right social structure of society, due to unplanned system of Indian civilization and its rapid disaster of population make the failure to face all kind of problems which make the society sufferer. Our India is still suffering from disaster like earthquake, floods, droughts, tsunamis etc. and we face the uncountable disaster of deaths from the beginning of humanity at the present time. In this research paper our focus is to make a Disaster Resistance Structure having the solution of dense populated urban cities area by high vertical expansion HYBRID STRUCTURE. Our efforts are to analyse the Reinforced Concrete Hybrid Structure at different seismic zones, these concrete frames were analyzed using the response spectrum method to calculate and compare the different seismic displacement and drift. Seismic analysis by this method generally is based on dynamic analysis of building. Analysis results shows that the Reinforced Concrete Building at seismic Zone V having maximum peak story shear, base shear, drift and node displacement as compare to the analytical results of Reinforced Concrete Building at seismic Zone III and Zone IV. This analysis results indicating to focus on structural drawings strictly at construction site to make a HYBRID STRUCTURE. The study case is deal with the 10 story height of a vertical expansion Hybrid frame structure at different zones i.e. zone III, zone IV and zone V having the column 0.45x0.36mt and beam 0.6x0.36mt. with total height of 30mt, to make the structure more stable bracing techniques shell be applied like mage bracing and V shape bracing. If this kind of efforts or structure drawings are followed by the builders and contractors then we save the lives during earthquake disaster at Bhuj (Gujarat State, India) on 26th January, 2001 which resulted in more than 19,000 deaths. This kind of Disaster Resistance Structure having the capabilities to solve the problems of densely populated area of cities by the utilization of area in vertical expansion hybrid structure. We request to Government of India to make new plans and implementing it to save the lives from future disasters instead of unnecessary wants of development plans like Bullet Trains.

Keywords: history, irresponsibilities, unplanned social structure, humanity, hybrid structure, response spectrum analysis, DRIFT, and NODE displacement

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Authors: Sung-Won Yoo, Chul-Hyeon Kang, Kyoung-Tae Park, Hae-Sik Woo

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Numerous studies were dedicated on the High Volume Fly-Ash (HVFA) concrete using high volume fly ash. The material properties of HVFA concrete have been the primordial topics of early studies, and interest shifted gradually toward the structural behavior of HVFA concrete such as elasticity modulus, stress-strain relationship, and structural behavior. However, structural studies consider small-scale members limited to the scope of reinforced concrete only. Therefore, in this paper, on the basis of recent studies on the structural behavior, 2 full-scale test members were manufactured with 7.5 m span length, fly ash replacement ratio of 50 % and concrete compressive strength of 50 MPa in order to evaluate the practicability of HVFA to real structures. In addition, 2 steel composite test members were also manufactured with span length of 3 m and using the same HVFA concrete for the same purpose. The test results of full-scale RC members showed that the practical use of HVFA on such structures is not hard despite small differences between test results and existing research results on the stress-strain relationship. The flexural test revealed very little difference between 50% fly ash concrete and general concrete in view of the similarity exhibited by the displacement and strain patterns. The experimental concrete shear strength being very close to that of design code, the existing design code can be applied. From the flexural test results of steel girder composite members, the composite behavior can be secured as much as that using normal concrete under the condition of sufficient arrangement of reinforcing bar.

Keywords: composite, fly ash, full-scale, high volume

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Authors: Hana' Al-Ghanim, Mu'tasim Abdel-Jaber, Maha Alqam

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This experimental investigation deals with shear strengthening of reinforced concrete (RC) deep beams using the externally bonded carbon fiber-reinforced polymer (CFRP) composites. The current study, therefore, evaluates the effectiveness of four various configurations for shear strengthening of deep beams with two different types of CFRP materials including sheets and laminates. For this purpose, a total of 10 specimens of deep beams were cast and tested. The shear performance of the strengthened beams is assessed with respect to the cracks’ formation, modes of failure, ultimate strength and the overall stiffness. The obtained results demonstrate the effectiveness of using the CFRP technique on enhancing the shear capacity of deep beams; however, the efficiency varies depending on the material used and the strengthening scheme adopted. Among the four investigated schemes, the highest increase in the ultimate strength is recorded by using the continuous wrap of two layers of CFRP sheets, exceeding a value of 86%, whereas an enhancement of about 36% is achieved by the inclined CFRP laminates.

Keywords: deep beams, laminates, shear strengthening, sheets

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Authors: Amit S. Chauhan, S. Mandal

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The structural response of shear walls subjected to various types of loads is difficult to predict precisely. They are incorporated in buildings to resist lateral forces and support the gravity loads. The steel plate shear walls (SPSWs) are used as lateral load resisting systems for buildings and acts as an alternative to reinforced concrete shear walls (RCSWs). This paper compares the behavior of SPSW with the RCSW incorporated in a building frame having G+6 storey, located in Zone III, using the technique of Equivalent Static Method (ESM) as per Indian Standard Criteria For Earthquake Resistant Design of Structures IS 1893:2002. This paper intends to evaluate several parameters such as lateral displacement at tip, inter-storey drift, weight of steel and volume of concrete with the alteration of the shear wall with respect to different types viz., SPSW and RCSW. The strip model employed in this study is a widely accepted analytical tool for SPSW analysis. SPSW can be modelled as truss members by using a series of diagonal tension strips positioned at 45-degree angles. In this paper, by replacing the SPSWs with the tension strips, the G+6 building has been analyzed using STAAD.Pro V8i. Based on the present study, it can be concluded that structure with SPSWs is much better then structure with RCSWs.

Keywords: equivalent static method, inter-storey drift, lateral displacement, Steel plate shear wall, strip model

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Authors: Rahal Nacer, Beghdad Houda, Tehami Mohamed, Souici Abdelaziz

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Although the shrinkage of the concrete causes undesirable parasitic effects to the structure, it can then harm the resistance and the good appearance of the structure. Long term behaviourmodelling of steel-concrete composite beams requires the use of the time variable and the taking into account of all the sustained stress history of the concrete slab constituting the cross section. The work introduced in this article is a theoretical study of the behaviour of composite beams with respect to the phenomenon of concrete shrinkage. While using the theory of the linear viscoelasticity of the concrete, and on the basis of the rate of creep method, in proposing an analytical model, made up by a system of two linear differential equations, emphasizing the effects caused by shrinkage on the resistance of a steel-concrete composite beams. Results obtained from the application of the suggested model to a steel-concrete composite beam are satisfactory.

Keywords: composite beams, shrinkage, time, rate of creep method, viscoelasticity theory

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Authors: Emdad K. Z. Balanji, M. Neaz Sheikh, Muhammad N. S. Hadi

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This paper presents results of an experimental investigation on the behaviour of Hybrid Steel Fibre Reinforced High Strength Concrete (HSFR-HSC) cylinder specimens (150 mm x 300 mm) under uniaxial compression. Three different combinations of HSFR-HSC specimens and reference specimens without steel fibres were prepared. The first combination of HSFR-HSC included 1.5% Micro Steel (MS) fibre and 1% Deformed Steel (DS) fibre. The second combination included 1.5% MS fibre and 1.5% Hooked-end Steel (HS) fibre. The third combination included 1% DS fibre and 1.5% HS fibre. The experimental results showed that the addition of hybrid steel fibres improved the ductility of high strength concrete. The combination of MS fibre and HS fibre in high strength concrete mixes showed best stress-strain behaviour compared to the other combinations and the reference specimens.

Keywords: high strength concrete, micro steel fibre (MS), deformed steel fibre (DS), hooked-end steel fibre (HS), hybrid steel fibre

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Authors: Thanh N. Do

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This paper addresses the modeling of two critical behaviors of concrete material in reinforced concrete components: (1) the increase in strength and ductility due to confining stresses from surrounding transverse steel reinforcements, and (2) the progressive deterioration in strength and stiffness due to high strain and/or cyclic loading. To improve the state-of-the-art, the author presents a new 3D constitutive model of concrete material based on plasticity and continuum damage mechanics theory to simulate both the confinement effect and the strength deterioration in reinforced concrete components. The model defines a yield function of the stress invariants and a compressive damage threshold based on the level of confining stresses to automatically capture the increase in strength and ductility when subjected to high compressive stresses. The model introduces two damage variables to describe the strength and stiffness deterioration under tensile and compressive stress states. The damage formulation characterizes well the degrading behavior of concrete material, including the nonsymmetric strength softening in tension and compression, as well as the progressive strength and stiffness degradation under primary and follower load cycles. The proposed damage model is implemented in a general purpose finite element analysis program allowing an extensive set of numerical simulations to assess its ability to capture the confinement effect and the degradation of the load-carrying capacity and stiffness of structural elements. It is validated against a collection of experimental data of the hysteretic behavior of reinforced concrete columns and shear walls under different load histories. These correlation studies demonstrate the ability of the model to describe vastly different hysteretic behaviors with a relatively consistent set of parameters. The model shows excellent consistency in response determination with very good accuracy. Its numerical robustness and computational efficiency are also very good and will be further assessed with large-scale simulations of structural systems.

Keywords: concrete, damage-plasticity, shear wall, confinement

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Authors: Fares Jnaid, Riyad Aboutaha

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In this paper, a nonlinear Finite Element Analysis (FEA) was carried out using ANSYS software to build a model able of predicting the behavior of Reinforced Concrete (RC) beams with unbonded reinforcement. The FEA model was compared to existing experimental data by other researchers. The existing experimental data consisted of 16 beams that varied from structurally sound beams to beams with unbonded reinforcement with different unbonded lengths and reinforcement ratios. The model was able to predict the ultimate flexural strength, load-deflection curve, and crack pattern of concrete beams with unbonded reinforcement. It was concluded that when the when the unbonded length is less than 45% of the span, there will be no decrease in the ultimate flexural strength due to the loss of bond between the steel reinforcement and the surrounding concrete regardless of the reinforcement ratio. Moreover, when the reinforcement ratio is relatively low, there will be no decrease in ultimate flexural strength regardless of the length of unbond.

Keywords: FEA, ANSYS, unbond, strain

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Authors: Seung-Ho Choi, Jae Yuel Oh, Chi Sung Lim, Ho Seong Jung, Kang Su Kim

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In recent years, various strengthening methods for buildings have been developed, but most of them require quite a long construction period during which the building users need to be patient on uncomfortable working environments including various lousy noises or even evacuation of the buildings. In this study, externally anchored precast wall-panel method (EPCW) for strengthening non-seismic reinforced concrete (RC) structures has been proposed, which is occupant-friendly technique because the strengthening walls are manufactured at factory and can be tightened to the members very quickly at the site. In order to investigate the structural performance of the specimens strengthened by the EPCW method, a total of four specimens were fabricated, and tested under axial and reversed cyclic lateral loads. The test results showed that the lateral resistances of the specimens strengthened by the EPCW method were greatly enhanced in both positive and negative directions, compared to the RC specimen having non-seismic details.

Keywords: precast wall, seismic strengthening, reinforced concrete, externally-anchored

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Authors: Salah Guettala, nesreddine.djafarhenni, Akram Khelaifia, Rachid Chebili

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This study assesses the impact of infill walls' layout in both plan and elevation on the seismic behavior of a 3D reinforced concrete structure situated in a high seismic zone. A pushover analysis is conducted to evaluate the structure's seismic performance with various infill wall layouts, considering capacity curves, absorbed energy, inter-story drift, and performance levels. Additionally, torsional effects on the structure are examined through linear dynamic analysis. Fiber-section-based macro-modeling is utilized to simulate the behavior of infill walls. The findings indicate that the presence of infill walls enhances lateral stiffness and alters structural behavior. Moreover, the study highlights the importance of considering the effects of infill wall layout, as non-uniform layouts can degrade building performance post-earthquake, increasing inter-story drift and risk of damage or collapse. To mitigate such risks, buildings should adopt a uniform infill wall layout. Furthermore, asymmetrical placement of masonry infill walls introduces additional torsional forces, particularly when there's a lack of such walls on the first story, potentially leading to irregular stiffness and soft-story phenomena.

Keywords: RC structures, infll walls’ layout, pushover analysis, macro-model, fiber plastic hinge, torsion

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Authors: Thamer Kubat, Riadh Al Mahiadi, Ahmad Shayan

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The alkali-aggregate reaction (AAR) in concrete has a negative influence on the mechanical properties and durability of concrete. Confinement by carbon fiber reinforced polymer (CFRP) is an effective method of treatment for some AAR-affected elements. Eighteen reinforced columns affected by different levels of expansion due to AAR were confined using CFRP to evaluate the effect of expansion level on confinement efficiency. Strength and strain capacities (axial and circumferential) were measured using photogrammetry under uniaxial compressive loading to evaluate the efficiency of CFRP wrapping for the rehabilitation of affected columns. In relation to uniaxial compression capacity, the results indicated that the confinement of AAR-affected columns by one layer of CFRP is sufficient to reach and exceed the load capacity of unaffected sound columns. Parallel to the experimental study, finite element (FE) modeling using ATENA software was employed to predict the behavior of CFRP-confined damaged concrete and determine the possibility of using the model in a parametric study by simulating the number of CFRP layers. A comparison of the experimental results with the results of the theoretical models showed that FE modeling could be used for the prediction of the behavior of confined AAR-damaged concrete.

Keywords: ATENA, carbon fiber reinforced polymer (CFRP), confinement efficiency, finite element (FE)

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Authors: E. Lam, Z. D. Yang, B. Li, I. Ho, T. Wong, V. Wong

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This paper reports some of the recent studies on strengthening of reinforced concrete members by ferrocement. Using mortar in ferrocement with high tensile strength, tensile properties of (high performance) ferrocement can be enhanced. In the proposed strengthening strategy, defective concrete cover of structural members is replaced by ferrocement so as to increase the load carrying capacity. This has been successfully applied to strengthen columns and beam-column joints. To facilitate the ease of application of the proposed strengthening strategy, mortar in ferrocement is applied through dry spray shotcrete.

Keywords: ferrocement, high performance ferrocement, dry, spray shotcrete, column, beam-column joint, strengthening

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Authors: Juan Bojórquez, Henry E. Reyes, Edén Bojórquez, Alfredo Reyes-Salazar

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This paper addressed the use of Artificial Intelligence to obtain the structural reliability of reinforced concrete buildings. For this purpose, artificial neuronal networks (ANN) are developed to predict seismic demand hazard curves. In order to have enough input-output data to train the ANN, a set of reinforced concrete buildings (low, mid, and high rise) are designed, then a probabilistic seismic hazard analysis is made to obtain the seismic demand hazard curves. The results are then used as input-output data to train the ANN in a feedforward backpropagation model. The predicted values of the seismic demand hazard curves found by the ANN are then compared. Finally, it is concluded that the computer time analysis is significantly lower and the predictions obtained from the ANN were accurate in comparison to the values obtained from the conventional methods.

Keywords: structural reliability, seismic design, machine learning, artificial neural network, probabilistic seismic hazard analysis, seismic demand hazard curves

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Authors: Rayed Alyousef, Tim Topper, Adil Al-Mayah

Abstract:

This paper presents results of an ongoing research program at University of Waterloo to study the effect of external FRP sheet wrap confinement along a lap splice of reinforced concrete (RC) beams on their fatigue bond strength. Fatigue loading of RC beams containing a lap splice resulted in an increase in the number and width of cracks, an increase in deflection and a decrease of the bond strength between the steel rebar and the surrounding concrete. The phase of the research described here consists of monotonic and fatigue tests of thirty two reinforced concrete beam with dimensions 2200⨉350⨉250 mm. Each beam was reinforced with two 20M bars lap spliced in the constant moment region of the tension zone and two 10M bars in the compression zone outside the constant moment region. The test variables were the presence or absence of a FRP wrapping, the type of the FRP wrapping (GFRP or CFRP), the type of loading and the fatigue load range. The test results for monotonic loading showed that the stiffness of all beams was almost same, but that the FRP sheet wrapping increased the bond strength and the deflection at ultimate load. All beams tested under fatigue loading failed by a bond failure except one CFRP wrapped beam that failed by fatigue of the main reinforcement. The FRP sheet increased the bond strength for all specimens under fatigue loading.

Keywords: lap splice, bond strength, fatigue loading, FRP

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Authors: Abdulsamee Halahla, Emad Allout

Abstract:

The purpose of this research is to study the behavior of exterior beam-column joints (BCJs) strengthened with ultra-high performance concrete (UHPC), in terms of the shear strength and maximum displacement using pushover analysis at the tip of the beam. A finite element (F.E) analysis was performed to study three main parameters – the level of the axial load in the column (N), the beam shear reinforcement (Av/s)B, and the effect of using UHPC. The normal concrete at the studied joint region was replaced by UHPC. The model was verified by using experimental results taken from the literature. The results showed that the UHPC contributed to the transference of the plastic hinge from the joint to the beam-column interface. In addition, the strength of the UHPC-strengthened joints was enhanced dramatically from 8% to 38% for the joints subjected to 12.8MPa and zero axial loads, respectively. Moreover, the UHPC contributed in improving the maximum deflection. This improvement amounted to 1% and 176% for the joints subjected to zero and 12.8MPa axial load, respectively.

Keywords: ultra high performance concrete, ductility, reinforced concrete joints, finite element modeling, nonlinear behavior; pushover analysis

Procedia PDF Downloads 105