P.C.J. Hoogenboom

Stringer Panel Model for Structural Concrete Design

A large number of concrete structures can be treated as two-dimensional plate problems. Both the load and the support reactions have lines of action that coincide with the plane of the structure. This is how beams, walls, dapped beams, corbels, etc., are analyzed. In practical design, two prominent methods of analysis exist: the strutand-tie method and the finite element method. First, we will briefly discuss the advantages and disadvantages of these two methods, and subsequently introduce a new method called the stringer panel model for the design of economic and rational reinforcement. This approach takes into account both equilibrium and compatibility and has the advantage of being highly design-oriented. An additional advantage of this method is that an estimation of the crack width in the serviceability limit state is part of the result.

Quadrilateral shear panel

Abstract Various models of structures and structural elements use an assembly of stringers and shear panels. The normal forces in the stringers can vary linearly and the membrane panels have constant shear. Often, these shear panels can be just rectangular but sometimes shear panels with a non-rectangular shape need to be used. In this paper a mathematical formulation is presented for a linear–elastic shear panel with a quadrilateral shape. The panel stiffness matrix is derived by the discrete element method, which yields a simple and efficient computational formulation. Comparison with finite element computations shows that the stiffness matrix is sufficiently accurate for engineering design.

Case-Study on the Application of Precast Double-Curved Concrete Elements for the Green Planet Shell Structure

Double-curved structures in general, and monolithic concrete shell structures more specifically, can transfer forces very efficiently. As a result, the thickness-to-span ratio can be very low, which, material-wise, can lead to a very economical design. However, the construction of shell structures is very labour-intensive and comes with high formwork costs and shells in modern building practice are rarely constructed. Concrete shell structures can be cast in-situ making use of temporary formwork and falsework, but they can be (partially) prefabricated as well, like the Palazzetto dello Sport in Rome. Although precasting is an effective technology for the repetitive production of concrete elements, for double-curved structures, having a large variety of shapes, the advantages of precasting seem to diminish quickly as a result of high formwork costs. Another disadvantage of precasting shell elements obviously seems to be the complexity of the required connections. For shell structures, the loss of stiffness of the connections might even lead to a crucial reduction of the buckling stability. A combination of both building methods, the prefabrication of the supportive structure and a finish with a cast in-situ layer, solves this before-mentioned issues and the advantages of both methods are combined: reduction of the complexity of the connections with an in-situ cast concrete layer and integration of the supportive structure in the design for a more cost-efficient erection. This paper describes the study of an innovative, partially precast, alternative solution for the construction of shell structures, and specifically addresses the influence of connections between precast elements on the overall shell behaviour. The Green Planet gas station along the A32 highway in The Netherlands was selected as a design case for such a building method.

Algorithm for Non-proportional Loading in Sequentially Linear Analysis

Sequentially linear analysis (SLA) is an alternative to the Newton-Raphson method for analyzing the nonlinear behavior of reinforced concrete and masonry structures. In this paper SLA is extended to load cases that are applied one after the other, for example first dead load and then wind load. It is shown that every nonlinear analysis step can be made in just two linear elastic analysis steps. The proposed algorithm is extremely robust, which is demonstrated in a prestressed concrete beam analysis. A comparison is made between results of SLA and Newton-Raphson with arch length control.

BUCKLING ANALYSIS OF OFFSHORE JACKETS IN REMOVAL OPERATIONS

In analysis of the removal of offshore jackets an important failure mode is buckling. In current practice, a buckling check involves manual determination of the buckling lengths of each frame member. It is estimated that 5 to 10% of the man-hours in structural analysis of removal projects is spend on checking and correcting buckling lengths. Fortunately, an alternative method is available that does not require determining buckling lengths. In this paper it is shown how this method can be derived from the NORSOK standard for tubular steel frame structures. The method is demonstrated in a removal analysis of an offshore jacket. It is concluded that this method can be successfully applied.Copyright