Cast Iron Beams Research Articles

Linear creep of bonded FRP-strengthened metallic structures at warm service temperatures

Ambient cured epoxy adhesive is widely used for bonding fibre reinforced polymer (FRP) plates to metallic structures. The present paper examines a typical strengthening adhesive to investigate the effect of adhesive thermo-viscoelasticity. The response of the adhesive was determined using a series of tests using the multi-frequency scanning mode of a dynamic mechanical analyser (DMA). The thermo-mechanical properties of the adhesive were then characterised using time–temperature superposition parameters and a Prony series representation for generalised Maxwell creep. The adhesive response was in turn used within two finite element (FE) models to examine the effect of creep in the adhesive at warm temperatures (<100 °C) on the performance of a lab-scale carbon fibre-reinforced polymer (CFRP) plate strengthened steel beam and a real-scale CFRP plate strengthened cast-iron beam respectively. The study found that thermo-viscoelastic creep of the adhesive bonding layer causes an increase in the slip between the FRP and the structure, which could induce damage in the bonded joint and make the CFRP becomes less effective, potentially resulting in failure of the strengthening system during the long-term service. Differential thermal expansion effects can enhance the joint bonding stress and allow the plate to maintain its contribution to the moment capacity of the beam; however, this benefit could be lost when temperature decrease, and the additional irreversible damage caused by the increased joint stress could reduce the effectiveness of strengthening further..

Strain determination based on strain gauge-guided radial basis function and digital image correlation

Two methods are proposed to determine structure surface strain fields in the presence of discontinuities. A partition inverse sequence calculation (PISC) method is presented to calculate displacement based on image matching from the second-last to first image, sequentially. The final deformed image is selected as a reference image, and several areas of interest are identified along the crack boundary prior to calculation. A strain gauge-guided partial derivative of a radial basis function (SPD-RBF) method is introduced to obtain strain distributions. Experimental data from strain gauges that adhered to specimen surfaces are applied to estimate shape parameter and obtain guided values, followed by strain calculation based on PD-RBF. Two typical experiments are conducted to verify the validity and accuracy of the PISC and SPD-RBF. Moreover, the proposed methods are successfully applied to evaluate the strain distributions at the crack tip of a cast iron beam. The experimental results further validate the applicability of the proposed methods in handling deformation with discontinuities.

Reliability based determination of material partial safety factors for cast iron beams in jack arched construction exposed to standard and natural fires

Cast iron beams were extensively used in many 19th century structures, especially in fireproof flooring systems (such as jack arch). Many such structures are still in use today and it is important that they fulfil the current requirements of fire resistance when there is a change of use. These structures are out of scope of modern design codes and old design codes do not provide guidance for fire resistance design. Furthermore, cast iron is a brittle material weak in tension, and there are many uncertainties in its mechanical properties at ambient and elevated temperatures due to material flaws. It is necessary to quantify the probability of structural failure and to introduce safety factors to reduce the probability of structural failure in fire to an acceptable level. This paper presents the results of a detailed study whose purpose is to derive appropriate safety factors to achieve different levels of reliability, for fire safety design of cast iron beams. In this study, a fibre analysis method has been used to calculate the moment capacity of four different types of cast iron cross section. Using randomized stress-strain-temperature relationships, based on variability of the different governing parameters (under tension: maximum stress, 0.2% proof stress, corresponding strains at maximum stress (strength) and failure; under compression: Young's modulus, proportional limit, 0.2% proof stress and the maximum stress), the probability distribution of moment capacity has been calculated. Based on the criterion of cast iron beam failure not exceeding probabilities of 10−1, 10−2 and 10−3, material safety factors of 1.5, 3.0 and 5.0 respectively have been obtained.

Moment capacity of cast-iron beams exposed to fire

Cast-iron girders were used in many nineteenth century structures, especially in fireproof flooring systems (such as jack arches). Many such structures are still in use today and it is important that they fulfil the current requirements on fire resistance when there is a change of use. Cast iron has limited ductility so it is not possible for cast-iron beams to achieve total plasticity as for modern steel beams. Furthermore, cast iron has different mechanical properties in tension and compression and there is often a severe non-uniform temperature distribution in cast-iron beam sections. This paper presents the development of a simplified method to calculate the bending moment capacity of cast-iron beams in a jack arched system exposed to a standard ISO 834 fire. The method is based on an assumed strain distribution in the cross-section. A comparison of the results calculated using the simplified method with those using the fibre method, validated by Abaqus simulation results, indicates that the proposed simplified method is sufficiently accurate as the basis of a design method.

Finite difference method–based calculation of gravity deformation curve for the large-span beam of heavy-duty vertical lathe

To solve the problem that gravity deformation curve of large-span cast-iron beam analyzed by finite element method simulation is inaccurate due to material imperfection, a discretization calculation considering the inhomogeneity of the material based on finite difference method is proposed. Supposing the flexural rigidity of the beam is different along the length, the continuous beam is discretized into segments based on finite difference method, and equivalent flexural rigidity is presented to characterize the inhomogeneity of the material. Correction model of bending deformation is constructed to revise the results of finite element method simulation applying equivalent flexural rigidity that could be obtained by combining the discretization model and deformation data acquired in a simple self-load experiment in which the beam is simply supported without any assembly process. Finally, flowchart of application is presented, and the approach is illustrated through an example from real case. The experimental results show that the computational accuracy is improved from 73.14% to 88.33%, compared with just finite element method simulation.

270 X-FEMによる偏心衝撃荷重を受ける鋳鉄梁の三点曲げき裂進展解析

270 X-FEMによる偏心衝撃荷重を受ける鋳鉄梁の三点曲げき裂進展解析

Briefing: William Fairbairn and the ‘suspended girder’

This briefing introduces the reprint of a classic paper presented to the Institution of Civil Engineers in April 1847 by William Fairbairn. A month earlier, Fairbairn had investigated the cause of a partial building collapse at Ancoats Mill in Manchester in which a mill worker had died. Contemporary newspaper reports on the accident and the inquest are used to put Fairbairn's paper into context. Some background is provided to Fairbairn's serious concerns about the safety of large buildings when not designed and built by competent persons. Much of the discussion at the Institution after presentation of the paper was taken up by the defence by leading railway engineers of the principle of the ‘suspended girder’, a cast iron beam strengthened with wrought iron trussing rods. Fairbairn blamed the mill building collapse mainly on the use of the suspended girder, which at the time was gaining popularity for railway bridges of longer span. The paper explains how events unfolded soon afterwards to prove Fairbairn right and his eminent contemporaries wrong.

Modélisation and influence of shear retention parameter on the response of cast iron beam

To obtain the complete solutions describing the balance of cast iron beam, it is necessary to introduce a behavioural law characterizing the physical properties of material. The goal of this work is to study the response of cast iron beam by taking into account the variation of the shear retention parameter (aggregate interlock) and the mesh density. The cast iron as a brittle material was assumed as elastic-plastic material and follow concrete model failure criterion with associated flow rule. The element includes a smeared crack approach for handling cracking in tension zones and a plasticity algorithm to account for the possibility of crushing in compression zones. The amount of shear transfer across a crack can be varied between full shear transfer and no shear transfer at a cracked section. This option is controlled by a coefficients β called shear retention factor and range between 0 (no aggregate interlock) to 1 (full aggregate interlock). It is also noted that the best choice of a shear retention factor play a significant role in the total response of the structure. The numerical results obtained are compared with other results obtained in the literature.

An improved closed-form solution to interfacial stresses in plated beams using a two-stage approach

Shear stress and normal stress in the thickness direction at interfaces (referred to as interfacial shear and transverse normal stresses, respectively, hereafter) have played a significant role in understanding the premature debonding failure of beams strengthened by bonding steel/composite plates at their tension surfaces. Due to the occurrence of dissimilar materials and the abrupt change of cross-section, the stress distribution at plate ends becomes singular and is hence considerably complicated. Extensive experimental and analytical analyses have been undertaken to investigate this problem. Large discrepancies have been found from various studies, particularly from experimental results due to the well-acknowledged difficulty in measuring interfacial stresses. Numerical analyses, e.g. 2-D or 3-D finite-element analysis (FEA), may predict accurate results, but they demand laborious work on meshing and sensitivity analysis. Analytical solutions, in particular those in a closed form, are more desirable by engineering practitioners, as they can be readily incorporated into design equations. This paper reports an improved closed-form solution to interfacial stresses in plated beams using a two-stage approach. In this solution, beams and bonded plates can be further divided into a number of sub-layers to facilitate the inclusion of steel bars or multiple laminae. Thermal effects may also be considered by using equivalent mechanical loads, i.e. equivalent axial loads and end moments. Numerical examples are presented to show interfacial stresses in concrete or cast iron beams bonded with steel or FRP plates under mechanical and/or thermal loads. The effect of including steel reinforcements with various ratios in the RC beam on interfacial stresses is also investigated. Compared with previously published analytical results, this one improves the accuracy of predicting the transverse normal stresses in both adhesive–beam and plate–adhesive interfaces and the solution is in a closed form.

The Birth of Prestressing? Iron Bridges for Railways 1830 to 1850

The new railways in Robert Stephenson's day needed many slim bridges with flat soffits. Simple cast iron beams sufficed for short spans but problems arose with jointing of castings for longer ones. A solution, with wrought iron ties added to bolted castings, seemed ideal and was widely adopted. The misconception with this scheme was not realised until after the disastrous failure of Stephenson's Dee Bridge at Chester in 1847. A major inquiry followed and extensive remedial work. New bridge forms emerged, notably Fairbairn's ungainly wrought plate girders. Charles Wild's development from the failed system was another. Here Wild successfully used the principle of prestressing on cast iron, some 80 years before Freyssinet 'introduced' it with concrete in the 1930s. Fairbairn's thinking had a wide following but the only application of Wild's design was his neatly detailed bridge over the Arno. Was Wild too far ahead of his time?

The Cast Iron Beams at Kew Bridge Pumping Station — Faithful Friends or Fickle Enemies?

The Cast Iron Beams at Kew Bridge Pumping Station — Faithful Friends or Fickle Enemies?

Strengthening two London Underground covered ways

Covered ways 12 and 58 are parallel covered ways carrying the District and Circle Lines of London Underground near the High Street Kensington Station. They were constructed in 1867 and support Kelso Place— a twin-ended cul-de-sac—and predominantly residential properties over the railway. The two covered ways are each approximately 110 m long, with interconnecting cross-passages. The roof comprises brick jack-arches spanning onto cast iron beams, 45 in each covered way. The cast iron beams were assessed for the building loads and highway loads, and found to be overstressed. Also, owing to the condition of the track, there had been a history of concerns by local residents relating to noise caused by the passage of trains through the covered ways. In order to improve the existing structure gauge clearances, the tracks were lowered. To minimise the overall construction depth and required track lowering, the new superstructure comprised ‘aerofoiľ-type semicircular steel beams erected within the jack-arches. Piled foundations were constructed in front of the existing piers and abutments to minimise any settlements that would have resulted following track lowering. New track supports were constructed over two sewer crossings in the covered ways. A new ballasted track bed was installed on a noise reduction mat.

Strengthening two London Underground covered ways

Covered ways 12 and 58 are parallel covered ways carrying the District and Circle Lines of London Underground near the High Street Kensington Station. They were constructed in 1867 and support Kelso Place— a twin-ended cul-de-sac—and predominantly residential properties over the railway. The two covered ways are each approximately 110 m long, with interconnecting cross-passages. The roof comprises brick jack-arches spanning onto cast iron beams, 45 in each covered way. The cast iron beams were assessed for the building loads and highway loads, and found to be overstressed. Also, owing to the condition of the track, there had been a history of concerns by local residents relating to noise caused by the passage of trains through the covered ways. In order to improve the existing structure gauge clearances, the tracks were lowered. To minimise the overall construction depth and required track lowering, the new superstructure comprised ‘aerofoiľ-type semicircular steel beams erected within the jack-arches. Piled foundations were constructed in front of the existing piers and abutments to minimise any settlements that would have resulted following track lowering. New track supports were constructed over two sewer crossings in the covered ways. A new ballasted track bed was installed on a noise reduction mat.

Mechanical and Nondestructive Testing to Verify the Effectiveness of Composite Strengthening on Historical Cast Iron Bridge in Venice, Italy

The oldest cast iron arch bridge built in 1852 in Venice exhibits serious deterioration due to corrosion and cracking of its members. The Municipality accepted a proposal to strengthen it with Aramid fiber reinforced polymers (AFRP) materials. The AFRP materials application aims to arrest cracks and reduce the structure’s vulnerability to impact by boats. Tests have already been performed on structural cast iron beams taken from similar cast iron bridges dismantled. Results from four point bending tests showed an increase in strength and a different fracture mode depending on FRP application. Charpy tests showed an increased fracture energy in specimens strengthened with FRP and primer. Utilization of bidirectional and triaxial fabrics was discussed. However this paper is particularly focused on nondestructive testing following the FRP application. Nondestructive testing has been planned both for laboratory test specimens and for a long term monitoring program. Artificial defects, embedded during manufact...

19TH CENTURY CAST-IRON BEAMS: THEIR DESIGN, MANUFACTURE AND RELIABILITY.

Many 19th century cast-iron beams are still in service in the UK, particularly in major public buildings in London, in textile mills and warehouses in northern England and in a variety of bridge structures. Their success is based on scientific study which laid the foundations for much of our present-day understanding of structures. This paper describes 19th century practice for the design, manufacture and testing of cast-iron beams and - by analysing contemporary reports of structural failures - shows that the decline in the use of cast-iron beams had less to do with mistrust of the material by engineers than is popularly believed.

Structural Engineering in the Lancashire Cotton Spinning Mills 1850-1914: the example of Stott &amp; Sons

Stott & Sons were one of the major firms of mill architects in Lancashire, being responsible for some 20% of new cotton spinning mills built between 1880 and 1914. Their early mills were Fairbairn type mills with single brick arches supported by cast iron columns and beams. After 1870 they developed this system further in order to provide a floor of minimum thickness with maximum free floor space and window area. To do this the new materials of rolled iron and then steel were used to replace the cast iron beams, although cast iron columns were retained. They continued to use brick arches but after 1890 began to use reinforced concrete floors as well, although other architects had already made the change by this date. In making these advances Stott & Sons obtained two Patents, in 1871 and 1885.

On the Rupture Strength of Cast Iron under Non-Uniformal Stress Distribution

Much work has so far been made on the problem of the strength and rupture of materials under non-uniformal stress distribution in such cases as bending, torsion and tension of notched bars. It is well known that the beams of gray cast iron can support 15-25% larger bending moment than the theoretical rupture moment calculated upon the maximum tensile stress hypothesis. This is attributed to the existence of non-uniformal stress distribution by bending, though the relation between the rupture strength and stress distribution is not clear.The author carried out some experiments about the influence of non-uniformal stress distribution on the rupture strength of cast iron by the bending test. Using rectangular specimens of different depths each specimen was measured regarding its rupture moment and strain on the surface.The results obtained are summarized as follows;(1) In static bending of gray cast iron, the ratio of the measured rupture moment Mb and the theoretical moment Mth, of which the latter was calculated upon the maximum tensile stress hypothesis, changes with increase of its depth h. Mb/Mth increases with decrease in h, and the rupture moment decreases to the theoretical value by increasing h.(2) The author defined the strain gradient. xε by xε=1/ε1(dε/dx)1, and found that there was relation between xε and Mb/Mth, where Mb/Mth=1+√δxε. The type of the relation as mentioned above was similar to that which was proposed by Siebel and Petersen on the fatigue strength of notched bars.(3) In the relation, δ is regarded as material constant. For the gray cast iron used in the present experiment, δ was about 0.25mm. This value was almost the same as that obtained by Stieler on the fatigue strength of notched cast iron.(4) The rupture moment of cast iron beams can not be calculated by the bending strength which is determined as material constant. The bending strength varies according to the stress or strain gradient in the beam.

Rupture of Cast Iron Beams under Bending

The stress distribution being taken into account, the rupture strength of cast iron beams of rectangular section under bending becomes, [numerical formula] where, MB=bending moment at rupture, b=breadth of the beam, h=height of the beam, nh=distance of the neutral axis from the surface of tension side, and σB=tensile strength under uniform stress. From stress-strain curves of compression and tension, the tension curve being somewhat extended, the moment-deflection curve and the rupture moment were calculated. These calculated values conform very closely with experiment.

鑄鐵梁の曲げによる破壊に就て

鑄鐵梁の曲げによる破壊に就て

Experiments to Ascertain the Strength of Cast-Iron Beams for Beam Engines

Experiments to Ascertain the Strength of Cast-Iron Beams for Beam Engines