Finite Element Program Research Articles

Seismic Performance Assessment of Deteriorated Two-Span Reinforced Concrete Bridges

This paper presents a nonlinear analysis procedure for the seismic performance assessment of deteriorated reinforced concrete bridges using a modified damage index. A finite-element analysis program, RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), is used to analyze deteriorated two-span simply supported reinforced concrete bridges. The new nonlinear material models for deteriorated reinforced concrete behaviors were proposed, considering corrosion effects as shown in a reduction in reinforcement section and bond strength. A modified damage index aims to quantify the seismic performance level in deteriorated reinforced concrete bridges. Several parameters of two-span simply supported deteriorated reinforced concrete bridge have been studied to determine the seismic performance levels. The newly developed analytical method for assessing the seismic performance of deteriorated reinforced concrete bridges is verified by comparison with the experimental and analytical parameter results.

Seismic vulnerability for irregular reinforced concrete buildings with consideration of site effects

The seismic vulnerability of building structures with setback irregularity should always be analyzed considering the effect of the site on the structure’s response. By considering the site effect, variation in the magnitude and distribution of seismic vulnerabilities can be obtained, specifically when more accurate analyses are performed using non-linear structural modeling. In this sense, the present study focuses on the quantification of the vulnerability of irregular reinforced concrete buildings resting on four soil types; hard rock (S1), very dense soil (S2), stiff soil (S3), and soft soil (S4). Structural modeling is carried through a finite element program. Nonlinear (pushover) analyses were conducted on the selected building models. Finally, the interest of considering the effect of the site classes on the seismic vulnerability of buildings is discussed. The outcomes show that sites (S2) and (S3) have identical damage probabilities with a maximum difference no greater than 3.7%. However, site (S4) shows the highest damage probabilities.

Behaviour of sintered fly ash aggregates and steel fibers on reinforced concrete slabs subjected to punching

In this study the optimum replacement percentage of sintered fly ash aggregates in M30 grade of concrete was identified based on 28 days cubical compressive strength value. The optimum replacement of Sintered Fly ash Aggregates (SFA) is 40 %. Before identifying the optimum replacement percentage, the SFAs were tested for suitability test such as crushing strength test, impact test and water absorption test. Further, the optimum 40 % SFAs in concrete is tested for punching shear on the Reinforced Concrete (RC) slabs for a dimension of 1000 mm x 1000 mm x 100 mm. In addition to know the effect of steel fibers in RC slabs subjected to punching. A hook ended steel fibers having an aspect ratio of 55, 80 and 100 is selected and varied by volume of concrete for the punching shear values on RC slabs. The RC slabs concrete contains aspect ratio of steel fibers 55 is varied for 0.25 %, 0.5 %, 0.75 % and 1 % for volume of concrete. In addition to that a constant volume of steel fiber 0.5 % is selected for the aspect ratios of 80 and 100 for the punching shear tests. The punching shear values for the RC slabs shows that partial replacement of SFAs and steel fibers in concrete enhances the punching shear strength. These experimental tested results are compared with finite element programming (ABAQUS) and international codes such as IS 456 and ACI 2011. The experimental punching shear results were higher when compared to international codes.

Design and manufacture of a self-supporting racing motorcycle seat made on carbon fiber

This work presents the design and manufacture of the structural tail (subchassis+seat) of a racing motorbike which has participated in the MotoStudent 2016 edition, held in October 2016 on the Alcañiz circuit, representing the University of Malaga. Two motorcycles were presented, one inside the Petrol category (4 stroke engine and 250 cc) and another one in the Electric category. It is a self-supporting structure that replaces the use of the traditional subchassis and seat, in order to save weight. As a material we selected a 2x2 twill carbon fabric 3K, 200 g/m2 and Resoltech 1070/1074 epoxy resin. The selected manufacturing process has been manual molding and vacuum bag. Taking into account the estimated fiber percentage, the properties of the elemental sheet of composite material have been estimated using micromechanical models. These properties have been implemented in the finite element program Patran-Nastran for the optimization of the part. Once it has been designed, a model of the part has been fabricated on MDF wood which has been used to manufacture the mold of the piece in fiberglass. The designed part was homologated by the organization of the competition. The developed part is 50% lighter that previous solution. The manufactured mold allows to produce more pieces with the consequent cost reduction.

Research on differential settlement monitoring of highway expansion based on BIM technology

In order to overcome the problems of long response time and high error in traditional settlement monitoring methods of highway, a differential settlement monitoring method based on BIM technology is proposed in this paper. According to the large-scale general finite element program and geotechnical theory, the numerical analysis model of highway expansion project is established to obtain the deformation value of highway expansion subgrade under different subgrade design parameters and subgrade materials. The differential settlement deformation mode and influencing factors of highway expansion are analysed. According to the analysis results, combined with SAR and BIM technology, the differential settlement of expressway expansion in the study area is monitored. The simulation results show that the response time of the proposed method is always less than 5 ms, the maximum monitoring error is only 0.067%, the response time is short and the monitoring error is small.

Performance assessment of Cruciform steel column: FEM simulation

In any type of structure, a column is one of the most important structural components. A column's principal function is to transmit loads by compressive action. Torsional buckling is the primary cause of the column's collapse. The cruciform column is the best choice for increasing the column stiffness and its axial capacity while simultaneously reduces the overall sectional weight. The analytical evaluation is performed in this research utilising the ABAQUS finite element programme. The conventional column section as well as two other cruciform column sections are examined and contrasted. In this research, the column's overall performance and buckling characteristics are assessed. When compared to conventional column sections, the Cruciform column sections yield substantial results. It is concluded that the flanged cruciform column section supports a greater load while simultaneously reducing the total weight and expense of the structure.

Effect of the connecting beam stiffness on the bracing limit for reinforced concrete slender columns in single and multi-story frames

Abstract The main purpose of this paper is to study analytically the behavior of slender reinforced concrete columns existing in sway and non-sway structures. The studied variables were the stiffness of the beam connected to the slender columns, the stiffness of the bracing columns, and the number of bays and stories in the structure model. The stability of slender columns was studied and the required limits for the lateral bracing were determined using a finite element program to perform buckling analysis, linear analysis, and geometric nonlinear analysis for the different frame structural models. All the results obtained in this study were compared to the available methods included in the different building codes and the methods suggested by other researchers. The results indicated that the minimum value of the bracing limit, required to restrain the slender column against the side-sway, depends on the stiffness of the connecting beams, number of stories, and number of bays. The required bracing limit decreases with increasing the beam stiffness and with increasing the number of bays. However, the required bracing limit increases with the increase of the number of stories in the structure.

Effect of variable amplitude block loading on fatigue crack growth

The objective is to study the effect of load blocks on fatigue crack propagation. To carry out this study, the finite element program DD3IMP will be used, with the fatigue crack propagation being controlled by the value of the plastic deformation at the end of the crack. The material used was the Ti6Al4V alloy obtained by the selective laser fusion manufacturing process. Regarding the studied load patterns, two types of High-Low load blocks and two types of Low-High load blocks were studied. A plane stress state was always considered and the influence of the contact between the crack flanks on the predicted FCG rate is highlighted by removing numerically the contact conditions. The transient behavior observed between loading blocks of different amplitude is strongly reduced or vanishes when the contact is neglected. For load blocks with high values of stress ratio, the predicted FCG rate in steady state regime is approximately the same considering or neglecting the contact of the crack flanks. On the other hand, for low values of stress ratio, the predicted FCG rate is lower when the contact of the crack flanks is considered, which is related with crack closure level.

Torsional performance of reinforced concrete beam with carbon fiber and aramid fiber laminates

In the presented research paper, investigated the torsional performance of reinforced concrete beams with light emissions grade of cement utilizing Carbon fiber and its relative investigation with aramid fiber, for its torsional conduct, utilizing both exploratory and insightful strategies. A distinctive example of its strips folded over RC beams and the torsional conduct of these restrengthened beams is considered. Carbon fiber (CF) is utilized as outside support. Reinforced concrete beam retrofitted with CF tried for torsional disappointment utilizing lever arms exposed to torque. The beams have dimensions of 150mm in width and 200mm in depth and 1 m long, as planned according to IS456-2000. Three bars are intended for a twist. Steel has a stronger ultimate strength but a lower density than aramid FRP, as well as being easier to install and requiring no interim support until it reaches its full strength. The impact of various sorts and designs of CF on the initial stage of breaking load, extreme load conveying limit, and disappointment method of the beam are thought about and its relative examination utilizing finite element programming with aramid fiber gives a better outcome for additional investigation.

NONLINEAR FINITE ELEMENT ANALYSIS OF MECHANICALLY ANCHORED REINFORCED STEEL I BEAMS

Aim: Steel structural elements can lose their strength in vehicle crashes, fire, fatigue, decay, humidity, etc. Consequently, their load-bearing capacities reduce considerably. A widely used strengthening method for steel beams is fiber-reinforced polymer strips or plates. One of the most important problems for this practice is sudden end-strip debonding due to the high normal and shear stress concentration. In this study, the structural behavior of deformed steel I-beams strengthened by carbon composites under bending was studied numerically. Using a commercial nonlinear finite element program (ABAQUS), a finite element model verified with the formerly executed experimental study was presented. To examine the effect of Mechanical Anchorage on large samples, a parametric study was carried out with the verified finite element model. In the parametric study, mainly three parameters were considered. Flange slenderness ratio (Bf/tf), web slenderness ratio (H/tw), and length to cross-sectional depth ratio (L/bf). Results derived from the nonlinear analysis revealed that the employment of the bolt anchorage increases the load capacity of the deformed elements and sustains the elements to resist more loads. However, the behavior and strengthening capacity of this practice is accordingly dependent on the flange slenderness ratio and web slenderness ratio of the proposed beam. Obtained results also indicate that the efficiency of mechanical anchorage in short-span beams is higher compared to the long-span beams.

GELENEKSEL VE MODÜLLER KOLON-KİRİŞ BİRLEŞİM BÖLGESİNİN FARKLI YÜKLEME DURUMUNDA SONLU ELEMANLAR YÖNTEMİYLE İNCELENMESİ

Aim: Damages to buildings as a result of earthquakes in our country and in the world; structural design can consist of concepts such as rigidity and ductility, as well as column-beam junction details. Column-beam connections of structures with a steel frame carrier system can be designed as a rigid connection where the moment is transferred by using bolts or welding connection tools, or as an articulated connection. In the literature and in practice, the column-beam junction detail in the bearing system can be made using two methods called modular and conventional methods. Method: In the study; the behavior of the column-beam connection under the effect of displacement-controlled load of the two-stories frame system constructed using a modular and conventional method was investigated using the Abaqus finite element program. Findings: The load-displacement values obtained from the finite element model, the stress distribution and the yield state in the joint area were compared according to the 100 mm vertical and 100 mm horizontal displacement-controlled loading condition of the bearing system created by using different methods. Conclusion: The developed modular frame system exhibited the strong column-weak beam principle, which is the desired system behavior according to the earthquake resistant building design principle. However, although the frame system created using the traditional method is more rigid and the load bearing capacity is higher than the modular frame system.

Analysis and Design of Piled Raft Foundation Taking into Account Interaction Factors

In a combined piled raft foundation (CPRF) both raft and piles take their share of the total load applied. However, in practice, the contribution of a raft in taking load is usually ignored and the load is assumed to be supported on piles. This way of CPRF becomes excessively conservative and uneconomical. To economize the design, relative load sharing of raft and piles in CPRF has to be found. In this connection, different simplified methods have been developed, each one with some limitations. In this study, three simplified methods have been applied to two cases of pile‐raft systems. The methods include Randolph, Poulos‐Davis‐Randolph, and modified Poulos‐Davis‐Randolph. The first case is a hypothetical case consisting of a 12 m × 12 m raft supported on a square group of nine piles. The second case study is an actual eight‐story building to be constructed in Peshawar, Pakistan. The building is supported on a pile‐raft system, with raft resting on very soft clay underlain by dense sand. The two case studies are also modelled in the finite element program PLAXIS 3D for comparison. The results of all the simplified methods are comparable with PLAXIS 3D. However, the Randolph method is much closer to PLAXIS 3D for the two cases studied. Furthermore, it is also shown that piles in a piled raft system can be used as “stress reducers” as well as a “settlement reducers.” Additionally, the effect of interaction factors is also evaluated with the s/d ratio as well as with varying soil stiffness. It was concluded that ignoring these factors leads to a very unsafe design of the pile‐raft system.

Numerical finite element simulation and structural behaviour of cold-formed steel members

Cold-formed steel (CFS) is going through an interesting phase of development. Thin-walled cold-rolled steel structures are adopted widely for low-mid rise construction. The CFS sections find its application, not for construction but alternate sectors too, such as automobile and aerospace applications. Many research on the CFS members have been conducted in past but yet there is a scarcity of research done for flexural members, especially under the 3-point loading scenario. Unlikely most common 4-point loading, in the case of 3-point loading the member is under gradient moment distribution as well as is exposed to uniform shear along the span of the member. This paper attempts to bridge this gap and explains the developed finite element (FE) model, validating the developed model, followed by a parametric study. Commercially available FE program ABAQUS was adopted for numerical simulations. An extensive parametric study was conducted considering, 7 geometric sections, having 12 spans and two grades of steel, making a total of 168 simulations. The member non-dimensional slenderness (λ) ranged from 0.40 to 2.17. Preliminary results of this research indicate the significant effect of geometry, grade and non-dimensional slenderness on member moment behaviour and capacity. A higher grade of steel is found to be more sensitive to the effects of non-dimensional slenderness.

Improving ductility behavior of sway-special exterior beam-column joint using ultra-high performance fiber-reinforced concrete

In the last decades, ductility of the joints becomes one of the most relevant issues in seismic design. Experiments show that the joints ductility is enhanced using additional transverse reinforcements. Thus, the design codes set requirements to attain the required level of ductility of joints including high amount of transverse reinforcement. However, the assemblage of many types of reinforcements causes implementations difficulties. This paper focuses on improving ductility of exterior beam-column joint (BCJ) using ultra-high performance concrete (UHPC) while dispensing the transverse reinforcements in the joint to overcome the implementations difficulties. A 3-D non-linear model using the finite element program ABAQUS is constructed and validated using published experimental data. After that, the model is used to conduct a parametric study that includes the main parameters affecting the behavior which include the beam to column depth ratio, the axial load ratio, and the longitudinal reinforcement ratio in column. The results of the parametric study are used to compare the behavior of sway-special joints and the joints strengthened with UHPC in terms of strength, ductility and the mode of failure. The results assure the ability of UHPC-strengthened joints to attain the required level of ductility and strength when compared to special moment resisting frame.

FLEXURAL SIMULATION ANALYSIS OF RC T-GIRDERS STRENGTHED WITH POLYURETHANE CEMENT-PRESTRESSED STEEL WIRE ROPES

To verify the effectiveness of polyurethane cement-prestressed steel wire ropes for flexural reinforcement of reinforced concrete T-girders, this paper conducts flexural test research on 12 pieces of T-girder specimens. Through the ABAQUS finite element program to build a model for numerical simulation, the results show polyurethane cement prestressed steel wire rope reinforcement can significantly increase the yield load and ultimate load of reinforced girders. Taking a girder in the test (20mm reinforcement thickness of polyurethane cement) as an example, yield load and ultimate load increased by 61.5% and 102.3% compared to unreinforced girder. The finite element model calculation results of T-girder bending reinforcement are in good agreement with the bending reinforcement test, and the error is only about 2%. For different strength concrete, the yield load increases slightly with the increase of concrete strength. For T-girders with different reinforcement ratios, the bearing capacity of strengthened girders changes significantly with the increase of longitudinal reinforcement ratio. The yield load of girders with reinforcement ratio of 1.82% and 1.35% is 29.84% and 65.85% higher than that of girders with reinforcement ratio of 0.91%. The yield deflection is 13.18% and 3.99% higher than that of girders with reinforcement ratio of 0.91%. It can be concluded that the bending reinforcement method of polyurethane cement prestressed steel wire ropes can effectively strengthen the main girder and ensure the structural safety.

A coupled electro-chemo-mechanical theory for polyelectrolyte gels with application to modeling their chemical stimuli-driven swelling response

Polyelectrolyte gels consist of a polymer network with charged functional side-groups, and a solvent with counter-ions filling the interstitial spaces in the network. Such gels respond to chemical signals such as the pH and the ionic strength of their external environment by substantial swelling or deswelling, which makes them attractive for use in a wide variety of applications including tissue engineering, drug-delivery, bioelectronics, valves and actuators for microfluidics, as well as small-scale soft-robotic applications. The physics driving the swelling and deswelling processes in these gels is complex because of the coupling of large deformations, simultaneous transport of solvent and ions into and within the gel, the influence of the ions in solution on the degree of ionization of the functional side-groups in the polymer network, and the cross-diffusion of the charged and neutral species. In this work we present a thermodynamically-consistent coupled electro-chemo-mechanical theory for polyelectrolyte gels which take these phenomena into account. We have numerically implemented our theory in a finite element program. Using this numerical capability, we present simulations of the transient swelling response of both anionic and cationic polyelectrolyte gels in response to variations in the pH and ionic strength of the environment, and show that our theory can quantitatively reproduce some corresponding experimental results available in the literature. We also show the practical utility of our theory and its attendant numerical capability by presenting simulation results for some interesting actuators made from polyelectrolyte gels.

Preparation and electrical properties of conductive asphalt concretes containing graphene and carbon fibers

Graphene is a promising material applied in the field of road. In this study, graphene and carbon fiber were added in the asphalt concretes to achieve the aim of the effect of electrical conductivity and thermal conductivity. Graphene played a complementary role in the overall conduction pathway. The distribution of graphene in asphalt could be observed by fluorescence microscope. Meanwhile, preparing the conductive asphalt mastic and mixing method of the conductive asphalt concrete were also investigated. DSR test was used to test the effect of graphene on the shear deformation resistance and creep performance of bitumen. CT images were introduced into finite element program for analyzing current density distribution of conductive asphalt concrete to obtain the appropriate gradation. The optimum content of conductive medium was determined by measuring resistivity of concrete and heat conduction coefficient. Pressure sensitive characteristics were also researched to evaluate the effect of stress on electrical conductivity. Based on the results, it was found that addition of graphene reduces the resistivity of concrete and improves the thermal conductivity.

Longitudinal bending behaviors of hot-rolled H-beams by quenching and self-tempering

Quenching has become popular in materials strengthening since the current construction market favors high strength steels. However, unexpected bending deformations were often observed in quenched H-beams. This type of defect has only occurred at the very front of some quenched H-beams, and it was hardly predictable what caused the deformation. The study therefore focused on the bending which might result from thermo-metallurgical-mechanical deformation by quenching rather than by hot-rolling. A few beam-front shapes frequently observed in H-beam manufacturing were modeled for quenching simulation. Time-dependent quenching was simulated using a finite element program ANSYS to analyze the effect of rapid heat treatment and consequent phase transformation on bending deformation. Theoretical approaches, e.g., heat exchange in quenching and latent heat released during phase transition, were included in this study. The calculation results were compared with the experimental findings to verify whether the simulation was effective in discovering the bending mechanism. Further simulation analyses were also conducted to understand what triggered the unexpected bending phenomenon.

Numerical Analysis of Stability of a Road Embankment Subjected to Floods

In the floodplains of the river Indus several road embankments have been failed due to the action of floods. The main motivation for this study is to analyse how much high floods a typical road embankment could sustain and to suggest remedies to prevent failure if the flood is exceptionally high. For this purpose, an 8 m high road embankment located in flood region of the Indus river was analysed for stability when subjected to 4 m and 7 m high floods. Numerical analysis was performed with finite element program PLAXIS 2D. The results showed that the road embankment was stable prior to occurrence of the flood. The road embankment became instable when it was subjected to flood water of 4 m. This implies that the road embankment might not withstand pressure of the flood water higher than 4 m. The analysis suggested that the road embankment could fail if the flood water is 7 m high. To stabilize the road embankment when subjected to 7 m high flood, rockfill berm was utilized on the downstream side. Optimization analysis was conducted to use minimum volume of rockfill in order to reduce costs. The findings of this study could be beneficial to practicing engineers involved in maintenance of road embankments in floodplains

Theoretical Study on the Flexural Behavior of Structural Elements Strengthened with External Pre-Stressing Methods

This study aims to strengthen the flexural behavior of structural elements with external pre-stressing tendons, thereby improving their load-carrying capacity and increasing their resistance against the external load. Different techniques were used to apply external pre-stressed strengthening to RC beams and RC frames. Seven identical RC frames were analyzed: an original sample without an external tendon, two strengthened samples with external tendons at the positive bending zone, two strengthened samples with external tendons at the beam–column connection zone, a strengthened sample with external straight line tendons along the beam and, finally, a strengthened sample with external U-shape tendons along the beam of the frame. The analysis and the results were obtained using ANSYS WORKBENCH finite element (FE) program. Comparisons were performed between these techniques to determine which technique is better for strengthening. The failure mode, vertical deflection, column stress, load-carrying capacity, and ductility of the samples were listed and analyzed under four-point vertical loading. The results show that using external tendons significantly increases the load capacity and the stiffness of structural frames. Moreover, the tendon in the beam zone is more effective than the tendon in the column zone.