Elastic shakedown limit of a steel lattice girder

This paper presents a solution for the problem concerning the behaviour of a steel lattice girder subjected to dynamic load pulses. The theory of shakedown is used in the analysis. It is assumed that such loads cause a non-elastic response which includes dissipation of energy causing deformations and residual forces developed in the structural members of the girder. At a certain intensity of these forces, the girder can react to subsequent load pulses without further dissipation of energy, behaving in the elastic region after shakedown. This condition is referred to as adaptation of the structure to assumed cyclic loading. Elastic shakedown limit is determined through a direct analysis of the girder's dynamic behaviour, i.e. by checking if energy dissipation decreases with loading cycles. This gives the number of load applications after which no further increase of the energy dissipation is observed. The existing permanent deformations persist and residual forces remain in the same state. The analysis takes into account the possibility that compressed members can buckle which may result in non-elastic, longitudinal and transverse vibrations of these members. Non-linear geometry of members is taken into account. Then a perfectly elastic-viscoplastic model of the material is used. The main goal is to determine the state of the non-elastic movements of the girder joints and the residual internal forces developed in the girder members after each load application. The values obtained in this way serve as the basis for describing the next loading cycle. It is possible to use the approach presented in the paper to evaluate the effects of accidental loads. Then it is checked whether a small number of repetitions of accidental load would result in exceeding the serviceability limit state criteria of the maximum permanent deformation or displacement and/or strain amplitudes. If so, the magnitude of accidental load is greater than the elastic shakedown limit. Some examples are given to illustrate the application of the theory of shakedown.

bridges over the river Kei

The article is the outcome of the author's long-standing interest in the number and variety of bridges that were built within a short section of the Great Kei River at Victoria Drift - in close proximity to the village of Komgha - over a 100-year period. The particular bridges under scrutiny - with their dates of construction - are as follows: Temporary Military Bridge, 1877 (no longer extant) Lattice Girder Wagon Bridge, 1879 Timber Railway Bridge, 1905 (only foundations remaining) Relocated Lattice Girder Railway Bridge, 1948 N2 SANRAL Concrete Bridge, 1977.

On-Site Experimental and Numerical Investigations of Latticed Girder Composite Slabs

In this study, on-site bending experiments which represented realistic and pragmatic engineering applications were performed to investigate the resistance, deflection, and cracking process of latticed girder composite slabs. Then, utilizing ABAQUS software, nonlinear finite element (FE) models were established to investigate the behavior of the slabs. The modeling took into account the contact between the precast and cast-in-place concrete interfaces. Additionally, a damage-cracking methodology was introduced to evaluate the crack opening width of the slab. The results demonstrated that the proposed numerical model was capable of reproducing the typical behavior of the composite slabs’ performance analysis. The experimental and numerical results demonstrate that the lattice girder composite slabs conformed to the requirement of existing design codes.

Experimental and Numerical Study of Lattice Girder Composite Slabs with Monolithic Joint

This paper studies the behavior of lattice girder composite slabs with monolithic joint under bending. A full-scale experiment is performed to investigate the overall bending resistance, deflection and the final crack distribution of latticed girder composite slab under uniformly distributed load. A finite element model is given for the analysis of the latticed girder composite slabs. The effectiveness and correctness of the numerical simulations are verified against experimental results. The experimental and numerical studies conclude that the lattice girder composite slabs conform to the requirement of existing design codes. A parametric study is provided to investigate the effects of lattice girder with following conclusions: (a) the lattice girder significantly increases the stiffness of the slab when comparing with the precast slab without reinforcement crossing the interface; (b) the additional reinforcement near the joint slightly increases the stiffness and resistance, while it prevents damage near the joint.

Structural Behavior of Floor Systems Made by Floor Plates—Mechanical Model Based on Test Results

In daily engineering practice, the execution of concrete slabs by the mean of precast floor plates is seen as a common and reliable way to create massive slabs. In the last few decades, however, there has been an evolution to flat slabs and other uses where important bending moments must be transferred over the joints between the floor plates. For this kind of application, there is a lack of knowledge and experimental evidence based on large-scale tests to define accurate failure and design models. In this work, a comprehensive overview is given of 20 large-scale tests and some additional tests to support the findings and observations. It is confirmed that a purely bending-based design of the joints delivers reliable results, but some conditions are set; first, the maximum distance of the lattice girder to the joint may not exceed 400 mm without voiding elements. Second, only a 95 mm distance must be respected with voiding elements or additional protruding reinforcement must be applied. Attention is also given to how the system works when the major components—adhesion, mechanical interlock, and friction—are missing at the interface. Finally, repair possibilities are discussed and how they should be designed.

Review of detail categories of lattice girder node joints of EC 3

<p>The paper deals with the re-evaluation of detail categories of lattice girder node joints based on fatigue test data. An elaborate database structure has been set up to evaluate the available fatigue test data in a differentiated way. Detail categories of different types of K and N joints have been investigated and re- evaluated based on the developed data base. Geometric influences on the fatigue strength have been analysed and design recommendations are given.</p>

Proposition of a simplified analytical design procedure for lattice girder slabs with shuttering in cold-formed steel lipped channel section

ABSTRACT This paper presents an analytical procedure to determine the resistance of a new composite ribbed lattice slab system, composed by a lipped channel cold-formed steel (CFS) profile in minor bending fastened to a lattice girder by plastic connectors, as well as light filling elements and additional rebar. Motivated by the lack of standardized procedures for such system, this paper combines slab design prescriptions to create a computational tool that estimates load capacity and required propping during construction, serving as a basis for a design catalogue. Finally, a strong limitation of unpropped construction due to the low performance of the cold-formed profile under minor axis bending was observed, being the system able to reach spans up to 1.5 m between props in general.

Experimental Study on the Application of Heat-Treated High-Strength Lattice Girder in Tunnel Engineering

Heat-treated high-strength rebar has many advantages, such as high strength, superior ductility, high yield ratio, excellent welding and cold bending performance, which can effectively reduce the amount of rebar and improve the project quality. Although heat-treated high-strength rebar has been successfully applied in many fields of civil engineering, its application in tunnel engineering is just getting started. In this study, the on-site test of axisymmetric heat-treated high-strength lattice girders in rail tunnels and road tunnels was carried out. Comparative analysis of the performance of axisymmetric heat-treated high-strength lattice girders and original-design I20b steel rib was conducted. The test results show that the settlement of high-strength lattice girders is decreased by about 7%~30% compared with the test section of original-design I20b steel rib. The surrounding rock pressure is similar, but the stress of high-strength lattice girders is slightly higher than that of I20b steel rib. Due to the better binding ability of the lattice girders and the concrete, the ultimate bearing capacity of the ‘lattice girders and shotcrete’ is greater than that of the ‘I20b steel rib and shotcrete’. Moreover, the steel consumption of lattice girder is about 36% less than I20b steel rib, which shows significant economic and social benefits.

Coura and Valença Bridges on Minho Railway line – old structures, updated performance

<p>The pleasant Minho railway single lane line section from Caminha to Valença crosses the Minho river at Valença, through a very interesting and beautiful steel bridge. At Caminha it crosses the river Coura, by an also attractive steel bridge. Both are more than a century old and were refurbished and upgraded in a recent past and had before severe speed restrictions and load limitations:</p><ol><li> <p>Coura bridge: This 1879 iron bridge is a 3 span 164m lower deck continuous closed lattice girder, for a live load of only 4t/m without dynamic effects allowance. It was totally supported by a new continuous steel arch bridge, so both work together, combining in a very elegant construction.</p></li><li> <p>Valença bridge: This double-deck 1886 bridge is a steel 5 span 333m continuous lattice girder. Pathologies like excessive bending on the columns top sections, changing inappropriate bearing and a lock-up system for the braking action resulted in a demanding but discrete reinforcement.</p></li></ol>