| 1. |
- Al-Gburi, Majid, et al.
(author)
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Reduction of Early Age Crack Risks in Concrete Walls by Using a New Casting Technique
- 2016
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In: Structural Engineering International. - : International Association for Bridge and Structural Engineering. - 1016-8664 .- 1683-0350. ; 26:3, s. 216-224
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Journal article (peer-reviewed)abstract
- Volumetric changes in early age concrete that are restrained might lead to cracks. The degree of restraint is influenced by the casting sequence and the dimensions of the castings. In the current study a new casting technique is proposed to reduce restraint in the newly cast concrete with a new arrangement of the structural joint to the existing old concrete. The proposed technique is valid for the typical structure wall-on-slab using one structural joint. This casting method means that lower part of the wall is cast together with the slab, and that part is called a kicker. Hereby, the behavior of the structure changes from a typical case wall-on-slab to a typical case wall-on-wall. It has been proven by the beam theory and demonstrated by numerical calculations that there is a clear reduction in the restraint from the slab to the wall using kickers. In the paper different kicker heights are studied with the aim of determining the minimum restraint in the upper part of the wall cast in contact with the kicker. The technique using kickers is compared with common measures used in the field to avoid cracking, such as cooling pipes in the new casting and/or heating cables in the adjoining old concrete. The presented method is both cost and time effective, as it opens the possibility to use larger structural length of each casting sequence.
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| 2. |
- Al-Gburi, Majid, et al.
(author)
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Using Artificial Neural Network to Predict the Restraint in Concrete Culvert at Early Age
- 2015
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In: Structural Engineering International. - 1016-8664 .- 1683-0350. ; 25:3, s. 258-265
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Journal article (peer-reviewed)abstract
- Estimation of restraint is very important for accurate prediction of the risk of concrete cracking at early age. The present study predicts the restraint in 324 walls and 972 roofs for a concrete culvert. A parametric study included the thickness and width of the roofs, thickness and height of the walls, thickness and width of the slab, and length of the structures. Each parameter increased or decreased the restraint in the walls and the roofs. The calculation of the restraint was done elastically by the finite-element method (FE). The results were used by an artificial neural network (ANN) tool, where firstly an influential percentage was investigated as input parameters on the restraint prediction. Equations have been derived by the ANN model to calculate the restraint in the walls and the roofs. It was then used in an Excel sheet to calculate the restraint and compare the result with the result from the finite-element calculations giving high accuracy between the ANN model and the FE calculations
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| 3. |
- Axelsson, Erik, et al.
(author)
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Effect of axle load spreading and support stiffness on the dynamic response of short span railway bridges
- 2014
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In: Structural Engineering International. - : IABSE. - 1016-8664 .- 1683-0350. ; 4, s. 457-465
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Journal article (peer-reviewed)abstract
- In dynamic analyses of railway bridges, the train axle loads are often modeled as moving point forces. However, one effect of the ballast is to spread these point forces. This can lead to large reductions of the bridge response, especially for short span bridges. For this reason, Eurocode prescribes to distribute the axle loads over three adjacent sleepers. In this paper, the axle load distribution is first studied using a plane finite element analysis and based on that, a triangular load distribution is proposed. Then, numerical simulations are performed to compare the effect of this load distribution with the Eurocode one. Both simply supported bridges and bridges with integrated backwalls, all with span lengths less than 10m, are studied. For the later bridges, the effect of the stiffness of the foundation has been studied by adding springs at the supports.
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| 4. |
- Crocetti, Roberto, et al.
(author)
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Timber Arch Bridges with V-shaped Hangers
- 2019
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In: Structural Engineering International. - : Informa UK Limited. - 1016-8664 .- 1683-0350. ; 29:2, s. 261-267
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Journal article (peer-reviewed)abstract
- The arch is a very efficient load bearing structure, especially when its shape is affine to the funicular of forces. However, if live loads are predominant as compared to permanent uniformly distributed gravity loads, the arch will be subjected to substantial bending moments, thus losing a great part of its structural efficiency. In traditional arch bridges with hangers arranged in a vertical manner, asymmetrical loads would cause a substantial deviation of the pressure line from the axial line of the arch. In this paper, an innovative concept for timber arch bridges is introduced where V-shaped hangers, rather than vertical hangers, are used. The adoption of V-shaped hangers significantly contributes to the reduction of the eccentricity between the pressure line and the axial line of the arch, thus decreasing the magnitude of bending moments in the arch. The paper discusses the advantages of using V-shaped hangers as an alternative to vertical hangers, both in terms of statics, in-plane stability and dynamic efficiency. Moreover, the design and the recent construction of a parabolic three-hinged arch made of timber, with a steel V-shaped hanger is thoroughly discussed in the paper.
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| 5. |
- Edskär, Ida, et al.
(author)
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Wind-Induced Vibrations in Timber Buildings-Parameter Study of Cross-Laminated Timber Residential Structures
- 2017
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In: Structural Engineering International. - : International Association for Bridge and Structural Engineering. - 1016-8664 .- 1683-0350. ; 27:2, s. 205-216
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Journal article (peer-reviewed)abstract
- A current trend (2016) to construct high-rise timber buildings is seen. In order to understand the limitations posed by the timber material, wind-induced dynamic behaviour causing vibrations in the serviceability limit state has to be studied. The aim of this research is to calculate the natural frequency and acceleration levels of timber buildings having a cross-laminated timber structure to further the understanding of its behaviour and how a change in parameters affects building performance as reflected against comfort criteria. The results were calculated through finite element modelling using commercial software and by performing a modal analysis. The parameters under scrutiny were material stiffness, wall density, damping ratio, building height, and building footprint. The results show that even at moderate building heights (12-14 storeys), the comfort criteria are not fulfilled. Furthermore, the interaction between stiffness and mass for timber buildings needs to be explored further. And since the change of building footprint has a strong influence on the dynamic behaviour, the interplay between architectural and structural design becomes more important. Finally, more data on measurements of damping in timber buildings need to be collected to further validate simulation models.
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| 6. |
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| 7. |
- Gottsäter, Erik, et al.
(author)
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Spatial Temperature Differences in Portal Frame Bridges
- 2020
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In: Structural Engineering International: Journal of the International Association for Bridge and Structural Engineering (IABSE). - : Informa UK Limited. - 1683-0350. ; 30:2, s. 254-261
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Journal article (peer-reviewed)abstract
- Thermal actions are considered in the design of bridges, as temperature variations can lead to restraint stresses and subsequent cracking. However, load descriptions are in some cases oversimplified or incompatible with modern applications, and background studies are limited. This paper therefore aims to develop a more detailed load description for the load case describing temperature differences between structural parts in bridges, focusing on portal frame bridges. The temperature in portal frame bridges is investigated by performing long-term thermal simulations using weather data from several locations in Sweden, and thereafter performing statistical analyses of the resulting temperature variations over time. The study gives suggestions of both characteristic and quasi-permanent values to be used in design based on the statistical analyses, and also notes a gradual change in temperature between structural parts, which could be considered in the design. The resulting quasi-permanent values are significantly lower than the values given in the Eurocode for temperature differences between structural parts, which, in turn, will lead to smaller and more realistic stress values in bridge design.
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| 8. |
- Hällmark, Robert, et al.
(author)
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Innovative prefabricated composite bridges
- 2009
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In: Structural Engineering International. - : Informa UK Limited. - 1016-8664 .- 1683-0350. ; 19:1, s. 69-79
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Journal article (peer-reviewed)abstract
- The competitiveness of composite bridges depends on different circumstances such as site conditions, local costs of material and staff, and the experience of the contractor. Two major advantages of composite bridges compared to concrete bridges are the ability of the steel girders to carry the weight of the formwork and the fresh concrete, and the shorter construction time which not only saves money for the contractor but even more for the road users. A further step is to prefabricate not only the steel girders, but also the concrete deck. In this paper, a new concept for composite bridges is described, with dry joints between the prefabricated concrete elements. The principal of the technique is presented, as well as some laboratory test simulating the load situation at an internal support in a multi-span bridge. Also, some experiences from an already built single span composite bridge with dry joints are presented.
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| 9. |
- Hällmark, Robert, 1981-, et al.
(author)
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Post-Installed Shear Connectors : Monitoring a Bridge Strengthened with Coiled Spring Pins
- 2019
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In: Structural Engineering International. - : Taylor & Francis. - 1016-8664 .- 1683-0350. ; 29:2, s. 225-233
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Journal article (peer-reviewed)abstract
- Traffic density and vehicle weight have been increasing over time, which implies that many existing road bridges were not designed for the high service loads and increased number of load cycles that they are subjected to today. One way to increase the traffic load capacity of non-composite steel–concrete bridges is to post-install shear connectors. This paper presents a study of a steel–concrete bridge that has been strengthened with post-installed coiled spring pins, a type of connector which can be installed from below while the bridge is still in service. The strengthening method and design procedure are presented, along with the results from field monitoring performed to evaluate the behaviour of the strengthened structure. The results from the strengthened and non-strengthened sections show that the coiled spring pins counteract the slip and increases the degree of composite action. Finite-element models of the field tests were created in order to compare the results using different design assumptions and establish a suitable level of detail for modelling the shear connectors.
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| 10. |
- Hällmark, Robert, et al.
(author)
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The behaviour of a prefabricated composite bridge with dry deck joints
- 2013
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In: Structural Engineering International. - 1016-8664 .- 1683-0350. ; 23:1, s. 47-54
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Journal article (peer-reviewed)abstract
- This paper describes the monitoring of a one-span composite bridge in northern Sweden. The bridge was built in 2000, with prefabricated deck elements connected to steel girders, and the back walls as well as the piers were also prefabricated. The monitoring was required to clarify the doubts regarding whether a bridge with dry deck joints can be expected to perform as a conventional composite bridge, with in situ cast deck and sections with sagging moments. To get a better understanding of the long-term structural behaviour, the bridge was monitored both during 2001 and 2011, instrumented with equipment measuring the deflections and strains in the steel cross section. The bridge was loaded with a truck in midspan having a total weight of 25 t. When the truck was centred between the girders, the results showed a symmetric behaviour, with respect to deflections and stresses. For the case with the truck stationed right above one of the steel girders, anti-symmetric behaviour was observed and studied by means of finite element calculations, taking into account the stiffness of the composite section as well as the end screens and the earth pressure below them.
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