Domagoj Matešan

Nonlinear Time-Dependent Analysis of Prestressed Concrete Shells

The numerical model for analysis of prestressed concrete plates and shells under short term and long-term static load are briefly presented. The model simulates the dominant nonlinear effects of concrete: the creep, shrinkage and aging, the development of cracks in tension and yielding in compression, and the changes in the tensile and shear stiffness in cracking zones. Reinforcing steel is modelled as a separate layer with anisotropic material properties i.e. with a possibility to transfer the stresses in the reinforcement bars direction only. Prestressing steel is simulated by 1-D curved element embedded in the shell finite element. A description of the tendon geometry, transfer of the prestressing effects from the tendon to the concrete, numerical modelling of the prestressing losses and the numerical procedure for analysis of the prestressing structures are briefly presented. The model is verified by comparison of the numerical results with the results of performed experimental test of prestressed concrete shell.

Numerical Model for Static and Dynamic Analysis of Masonry Structures

Firstly, the main problems of numerical analysis of masonry structures are briefly discussed. After that, a numerical model for static and dynamic analyses of different types of masonry structures (unreinforced, reinforced and confined) is described. The main nonlinear effects of their behaviour are modelled, including various aspects of material nonlinearity, the problems of contact and geometric nonlinearity. It is possible to simulate the soil-structure interaction in a dynamic analysis. The macro and micro models of masonry are considered. The equilibrium equation, discretizations, material models and solution algorithm are presented. Three solved examples illustrate some possibilities of the presented model and the developed software for static and dynamic analyses of different types of masonry structures.

Behavior of fiber reinforced mortar composites under impact load

This paper presents results of the experimental study on the behavior of plain and fiber reinforced cement mortars with different fibers under static and impact compressive load. Glass, polypropylene and carbon fibers were used in equal dosage by mass. The impact test was conducted using an impact tower with drop hammer, which represented the modification of the split-Hopkinson pressure bar system, with strain rates ranging from approximately 35 to 60 s-1. The results of the static test and impact test with two different drop heights were compared and discussed. Among other, it has been concluded that the tested fiber reinforced mortars had no greater static and impact strength compared to the plain mortar. Only their ductility was increased at both static and impact failure. Strengths and ductility of all composite specimens were similar, i.e. without the effect of fiber type. With the increase of strain rate, compressive strength is increased and ductility is decreased for all tested specimens.

Comparison of Developed Numerical Macro and Micro Masonry Models for Static and Dynamic Analysis of Masonry-infilled Steel Frames

First, the basic characteristics of macro and micro masonry models in numerical analyses of masonry structures are discussed. Afterwards, developed numerical macro and micro masonry models, intended for the nonlinear static and dynamic analysis of unreinforced and confined masonry walls, as well as of masonry-infilled frames, are briefly presented. The models are tested on previously performed experimental tests of masonry-infilled steel frame under horizontal static force and masonry-infilled steel frame on a shake-table. The precision of both models is compared. It is concluded that both numerical models can provide reliable results. However, the macro model has more advantages for wide practical application.

Numerical model for analysis of stress-ribbon bridges

U radu je prikazan razvijeni numericki model za analizu prednapetih provjesenih mostova opterecenih kratkotrajnim statickim, dinamickim i dugotrajnim opterecenjenjima i djelovanjima. Model simulira najvažnije nelinearne efekte ponasanja takvih konstrukcija, ukljucujuci nelinearno ponasanje gradiva, promjene geometrije konstrukcije, nastajanje konstrukcije u fazama, prednapinjanje i sl. Prikazana su osnovna rjesenja provjesenog mosta preko rijeke Cetine kod Zadvarja, te neki rezultati njegovog proracuna s pomocu razvijenog numerickog modela.

Stirrup effects on compressive strength and ductility of confined concrete columns

The results of experimental testing of stirrup effects on compressive strength and ductility of axially loaded confined reinforced concrete columns of rectangular cross-section are presented. Effects of different concrete strengths, different stirrup bar diameters and different stirrup spacing on columns bearing capacity and ductility have been researched.

The Use of Limestone Sand for the Seismic Base Isolation of Structures

The possibility of the use of a layer of natural material under foundations for seismic base isolation was investigated. The dissipation of seismic energy of a low-cost natural material with adequate thickness, bearing capacity, and lateral and vertical stiffness, which can serve as an optimal solution for seismic base isolation under the foundations of many structures, was tested. This paper presents the results of a brief experimental study to determine the effectiveness of ordinary limestone sand under the foundation of a cantilever concrete column to increase its seismic resistance. The behavior of small-scale columns with three substrates below the foundation (rigid base, the thin layer of limestone sand, and the thick layer of limestone sand) was investigated by the shake table. The column was exposed to a set of horizontal base accelerations until structure collapse. It was concluded that a layer of limestone sand of appropriate thickness and compressibility can serve as the means a seismic base isolation. The nonlinear numerical model for the dynamic analysis of planar concrete structures coupled with soil is briefly presented and verified by the performed experimental tests.

Passenger terminal extension structure at Split Airport

The main load-carrying structure, to be built as an extension to the passenger terminal building at Split Airport, is presented in the paper. The structure is complex and comprises various types of facilities (building, bridge, membrane shed), various load-bearing systems (space truss, space frame, dome, tensioned cable, tensioned membrane), various materials (reinforced concrete, structural steel, laminated wood, canvas, steel cable), and different activities (new construction, rehabilitation). When creating load-bearing structural assemblies, a significant emphasis was placed on architectural shaping. Structural design was made in accordance with prevailing regulations, standards, and rules of professional practice, at an advanced technical level.

The Effect of the Bedding Length of Lintel in Masonry Walls on Their Load Bearing Capacity

By using the previously developed numerical model of the authors for both, static and dynamic analysis of concrete and masonry structures, which can simulate their main nonlinear effects, the influence of the bedding length of lintel on the ultimate bearing capacity of some masonry walls with openings has been investigated. Three-storey masonry walls with door openings were analyzed. Unreinforced and confined masonry walls were considered. There were separately analyzed masonry walls under horizontal static forces at the floor levels and masonry walls under earthquake. The bedding length of the lintel reinforcement and quality of the masonry were varied. Characteristic displacements of the walls and crack states in the lintel’s area are presented. Finally, main conclusions and recommendations for practical application are given.

Nonlinear Creep Model for Concrete in Analysis of Plates and Shells

A numerical model for analysis of reinforced and prestressed concrete plates and shells including creep, shrinkage and aging of concrete, already developed by the authors, has been updated with a nonlinear creep model for concrete. The model can be applied for all levels of concrete stresses, while its use for ultimate stress levels is still not fully tested. The presented nonlinear concrete creep model is simple, based on the well known linear model of concrete creep, and intended for simulation of practical concrete structures. For the verification of the presented model, an experimentally tested square concrete plate and cylindrical prestressed concrete shell were analysed numerically. The results of experimental tests at high stress levels and numerical results show good agreement.