Rehabilitation of Hybrid RC-I Beams with Openings Using CFRP Sheets

This research presents an experimental investigation of the rehabilitation efficiency of the damaged hybrid reinforced concrete beams with openings in the shear region. The study investigates the difference in retrofitting ability of hybrid beams compared to traditional beams and the effect of two openings compared with one opening equalized to two holes in the area. Five RC beams classified into two groups, A and B, were primarily tested to full-failure under two-point loads. The first group (A) contained beams with normal weight concrete. The second group (hybrid) included beams with lightweight concrete for web and bottom flange, whereas the top flange was made from normal concrete. Two types of openings were considered in this study, rectangular, with dimensions of 100×200 mm, and two square openings with a side dimension of 100 mm. A full wrapping configuration system for the shear region (failure zone) was adopted in this research. Based on the test results, the repaired beams managed to recover their load carrying capacity, stiffness, and structural performance in different degrees. The normal concrete beam regains its total capacity for all types of openings, while the hybrid beams gain 84% of their strength. The strength of hybrid concrete members compared with normal concrete is 81 and 88% for beams of one opening and two openings, respectively. Doi: 10.28991/CEJ-2022-08-01-012 Full Text: PDF

Influence of Fatigue Crack Formation and Propagation on Reliability of Steel Members

During the years of bridge exploitation, many degradation processes and external influences attack its structure. Therefore, bridge reliability and durability is decreasing in time. On the other hand, the traffic load remains almost the same or even higher than in the past. However, bridges should not to become the limiting component of communication capacity and traffic reliability. Regarding to reliability, bridges should be assessed from the viewpoint of the Ultimate Limit States (ULS) and Serviceability Limit States (SLS). Within the ULS, cross-sections and members are verified for various types of stressing and their combinations, and also for fatigue at the same time. The cross-sectional verification, e.g., for bending stresses and fatigue, is done independently according to corresponding criteria of the ULS determined for strength verification a fatigue assessment separately. The presented article deals with the steel railway plate girder bridge with bottom member deck, in which there is an effort to prove the effect of the crack in tension bottom flange due to fatigue stressing on the change of bending resistance over time. The analytical calculation was derived and at the same time, the probabilistic approach of the influence of the fatigue crack size on the change of the cross-sectional resistance and reliability over time was used.

Flexural Strength Estimation for Hollow Cross-Section Simply Supported UHPC Beams

The hollow structural elements occupy a great deal of researchers’ interest due to the possibility of losing their weights and maintaining or developing their resistances especially when increasing both compressive and tensile strength of modern materials. The flexural strength based on the forces balance and stain compatibility was derived. Nine beams of Ultra High Performance concrete (UHPC) and conventional reinforced steel bars were casted. Several parameters were taken which are the thickness of the concrete top flange, thickness of the concrete bottom flange, depth of the longitudinal hollow and the ratio of the longitudinal reinforcing steel. By comp aring the practical and theoretical results, the proposed flexural strength provided a safety factor of one-fifth against the experimental collected data. The ultimate flexural force developed up 260 % when increasing the reinforced steel area 4.6 times and 230 % comparing with the solid beam. Many aspect ratios were also mentioned that keep the strength in developing.

Push-Out Test and FEM Analysis of Continuous Shear Connector

Composite steel concrete bridges with embedded continuous shear connectors are one of the newer popular options for short span (up to 20 m) bridges. They can be used for both road and railway bridges and due to their low structural height, nowadays, they are also a welcome alternative for bridge reconstructions – the concrete part serves as the bridge deck as well as the main structure. Unfortunately, In the Slovak Republic, no such bridges have been built as of yet (2020). At Technical University of Kosice, Department of Steel and Timber Structures, an extensive research regarding the steel shear connectors have been launched. Its goals are to bring new, easier for construction (due to prefabrication process), more resistant with even lower structural height, and more economical (due to lesser usage of materials and quick construction) geometrical solutions for composite steel concrete bridges as well as to open and popularize this solution for developers in the Slovak Republic. In this article, one of the new types is presented. It has a cross-section in a shape of a trapezoid, with holes in all its sides, except the bottom flange. Their purpose is to create concrete studs and secure full shear transmission with higher shear resistance, but they also serve to create space for transverse reinforcing bars. Its geometrical and material characteristics are closely specified. Results and process of push-out tests performed in Laboratory of Excellent Research onto three specimens are described and compared to results of finite element analysis simulation performed in Abaqus software.

Finite Element Analysis of Overlapped Z-Purlins Restrained by Sheeting

Cold-formed steel Z-purlins with overlapping at the intermediate supports ensures the continuity of the bending moment. A continuous beam with two equal spans of 6 m is investigated under gravity loading using the finite element method. The numerical model includes the beneficial interaction between the Z-purlins and the trapezoidal sheeting. Finite element results show that the screw spacing and sheeting thickness has a limited influence on the resistance of the member. The effect of the overlapping length and detailing of the connection is studied through a parametric study. Six overlaps varying from 100mm to 1200mm (1.6% to 20% of one span) capture the change of the failure mode from the overlap edge to the support region of the purlin. The connection detailing is studied considering multiple bolt/screw patterns. The detailing and length of the overlap connection has a major influence on the moment distribution and consequently on the failure mode. The detailed finite element analysis shows that assuming the beam connection as continuous in 1D beam models lead to an unrealistic bending moment distribution and failure mode. Connecting the bottom flange using screws improves the overall load carrying capacity of the beam especially for short overlap lengths. The increase in resistance is attributed to the restraining effect on the free flange which fails due to distortional buckling.

ANALISA KAPASITAS SAMBUNGAN KOLOM-BALOK BAJA MENGGUNAKAN STIFFENER PADA BALOK DENGAN CBFEM METHOD

CBFEM method adalah metode analisa finite element untuk menganalisa sambungan kolom-balok dengan memodelkan elemen sambungan secara detail dan presisi, dimana setiap elemen (plates and bolts) pada sambungan dihasilkan analisa tersendiri dengan FEA. Pada artikel ini disajikan hasil analisa kapasitas sambungan kolom-balok (sambungan baut) berdasarkan AISC 360-16 (ANSI/AISC 360, 2016) menggunakan CBFEM method dengan program bantu yaitu software IDEA Statica 2.1. Penentuan elemen-elemen sambungan (dimensi dan ukuran) menggunakan ketentuan dalam ANSI/AISC 358 “prequalified connections for special and intermediate frame for seismic applications”. Dari hasil analisa yang dilakukan dengan software IDEA Statica 2.1, didapatkan bahwa dengan menggunakan stiffener dapat mengurangi tegangan-regangan yang terjadi pada web balok, akan tetapi meningkatkan tegangan dan regangan yang terjadi pada top flange dan bottom flange. Untuk kapasitas sambungan tidak menimbulkan peningkatan yang signifikan. Kata kunci : CBFEM method, stiffener, web, flange, vertical bracket

FEM Study of a Steel Corrugated Web Plate Girder Subjected to Fire

The main aim of this work is a computational nonlinear analysis of a high strength steel corrugated-web plate girder with a very detailed and realistic mesh including vertical ribs, all the fillet welds and supporting areas. The analysis is carried out to verify mechanical structural response under transient fire temperature conditions accounting for an efficiency and accuracy of three various transient coupled thermo-elastic models. All the resulting stress distributions, deformation modes and their time variations, critical loads and eigenfrequencies as well as failure times are compared in all these models. Nonlinearities include material, geometrical and contact phenomena up to the temperature fluctuations together with temperature-dependent constitutive relations for high strength steel. They result partially from steady state and transient experimental tests or from the additional designing rules included in Eurocodes. A fire scenario includes an application of the normative fire gas temperature curve on the bottom flange of the entire girder for a period of 180 minutes. It is computed using sequentially coupled thermo-elastic Finite Element Method analyses. These account for heat conductivity, radiation and convection. The FEM model consists of a combination of 3D hexahedral and tetrahedral solid finite elements and uses temperature-dependent material and physical parameters, whose values are taken after the experiments presented in Eurocodes. Numerical results presented here demonstrate a fundamental role of the lower flange in carrying fire loads according to this scenario and show a contribution of the ribs and of the welds to the strength of the entire structure.

Compatability Behaviour on Cold Formed Steel for I Section and C Section in Variable Parameters

This Study represents compatibility on Cold formed steel in I-Section beams and C-section beams with variable length parameters was 1000mm, 1500mm, 2000 mm under simply supported end condition subjected to uniformly distributed loading. The Cold formed steel is of shell type in Numerical simulation is carried out using the Software ABAQUS. For validation the series of parameters studies have been carried out using the numerical model of different parameters, such as the effect of length, width, thickness. CFS I-Section steel in various thickness of 1mm, 2mm, 3mm and 4mm with same loading conditions. CFS C-Section steel in various uneven flange width such as 500mm at the top flange and bottom flange of different width such as 400mm, 300mm, 200mm respectively in variable lengths with various loading conditions and with the thickness of about 1mm. For both I-Section and C-Section Beams the Effective Length ranges, MISES(max and min) and deflections(max and min) were taken for the analyse of the Sections. This study gives the way of finding the effective Section by the analysis of behaviour of I-Section beam and C-Section beam through the deflection results in various length variations in the beam Section using the ABAQUS software for finding the Structural behaviour in the more accuracy manner by applying meshing more finer for the Element Section in the Analyse of beam. The loading condition and the supporting condition applied to the beam section in different loading for getting the effective Section. For further stability in effective section we can use different types of connection.

Experimental Study on Mechanical Performance of U-Shaped Steel-Encased Concrete Composite Beam-Girder Joints

This paper proposes a novel U-shaped steel-encased concrete composite beam-girder joint (referred to herein as the novel composite beam-girder joint), in which the U-shaped beams at two sides (L and R) are inserted into a shaped sleeve, and the U-shaped girder and two U-shaped beams are connected by the shaped sleeve through welding. Compared with the traditional beam-girder joints, the novel composite beam-girder joints take advantage of easy construction, light weight, and short construction period. The failure patterns, load-strain and load-deflection curves, and strain distributions of the novel composite beam-girder joints were investigated through the static loading tests on two full-scale specimens, denoted as GBJ1 and GBJ2. The two specimens were varied in beam section reinforcements. Specimen GBJ2 was equipped with 3Ф16 additional bars in the U-shaped beams based on Specimen GBJ1. Test results show that the two specimens failed as the through arc cracks developed at the concrete slab interfaces. The additional bars can increase the bearing capacity slightly but will also increase the stress concentration on the bottom flange of the shaped sleeve, leading to the decrease of ductility for Specimen GBJ2. The slab effect is considered in the test and can thus reflect the actual stress state of the beam-girder joints well. This study can provide a reference for the design and application of beam-girder joints.