João Alberto Venegas Requena

Theoretical and experimental analysis of RHS/CHS K gap joints

This work presents a study of welded K joints with gap, formed by a structural steel hot rolled hollow section, having rectangular hollow sections at the chords and circular hollow sections in the others members. The study developed theoretical and numerical analyses for the joints, experimental tests in full scale prototypes. Theoretical analyses were performed using code standards for K joints. The results in terms of behavior, ultimate load and collapse mode were analyzed and compared with numerical (finite elements) and theoretical models. The theoretical analysis was carried out from the code regulations. The joints tested indicated the failure mode of Plastic failure of the chord face (mode A). The results showed that the loads using code regulations and the ones from the numerical analysis had good agreement for the K joint.

Composite Hollow Truss with Multiple Vierendeel Panels

The aim of this study was to evaluate through analytical calculation, two-dimensional elastic modeling, and three-dimensional plastic modeling, the bearing capacity and failure modes of composite hollow trusses bi-supported with a 15 meter span, varying the number of central Vierendeel panels. The study found the proportion span/3 - span/3 - span/3, as the ideal relationship for the truss - Vierendeel - truss lengths, because by increasing the proportion of the length occupied by the central Vierendeel panels, the new system loses stiffness and no longer supports the load stipulated in the project. Furthermore, they can start presenting excessive vertical displacements and insufficient resistance to external shear forces acting on the panels.

Análise numérica-experimental de treliças tubulares planas para coberturas padronizadas para grandes vãos

The purpose of this study is the comparison between experimental and numerical data of a roof system made of tubular steel sections. Such roof system is applied mainly for supermarkets, large stores and industries. To evaluate the structural behavior of this system, a 900m2 prototype was built, - an unprecedented opportunity in Brazil to accomplish experimental tests with usual loads for this type of structure. Evaluating the behavior of the entire structure, with all the results obtained on experimental tests and numerical analysis, it was concluded that the prototype is in general accordance with the designed model in terms of stresses and displacement.

The effect of support springs in ends welded gap hollow YT-joint

This paper presents an analysis on the effect of support springs in an ends circular hollow sections welded into a YT joint. The overall behavior and failure of the joint were characterized under axial compression of the lap brace. Two joint failure modes were identified: chord wall plastification (Mode A) and cross-sectional chord buckling (Mode F) in the region below the lap brace. The system was modeled with and without support springs using the numerical finite element program Ansys. Model results were compared with experimental data in terms of principal stress in the joint intersection. The finite element model without support springs proved to be more accurate than that with support springs.

BEHAVIOR ANALYSIS OF BAR GAPS IN WELDED YT-JOINTS FOR ROLLED-STEEL CIRCULAR HOLLOW SECTIONS

We present a parametric analysis of gap variation between the lap brace and through brace of YT welded joints for rolled-steel circular hollow sections on plane steel structures. Our aim is to investigate the collapse behavior of YT-joints under lap brace axial compression. In particular, we focus on e/d0 ratios above 0.25 so bending moments can be taken into account during the design. We find that joint failure is primarily due to chord wall plastification (Mode A) and cross-sectional chord buckling (Mode F) in the region underneath the lap brace. Our joint design followed the Limit States Method, and our results were based on a comparative analysis of three different methods: an analytical solution derived from a set of international technical norms, an experimental analysis, and numerical modeling using Ansys as calibrated by our experimental results.

Influence of shear lag coefficienton circular hollow sections with bolted sleeve connections

The circular hollow sections (CHS) are being widely employed in steel structures around the world, increasing the development of new researches. This article proposes an innovative connection model for circular hollow sections that facilitates and reduces the assembly cost of hollow section structures. The proposed connection is a tube sleeve, used to splice two tubes, composed of an inner tube with a diameter smaller than the connecting tubes, which is connected to the outer tubes by bolts passing through both tubes. This connection can be a cheaper and easier alternative to flange connections, which are widely used in large span tubular trusses. The connection was tested in laboratory under tension loading. The tests made it possible to identify the influence of stress distribution on tubes and the need for the use of a shear lag coefficient. The results of the ultimate load capacity demonstrated the viability of the tube sleeve connection use.

Numerical methodology for analyses of tubular KK multiplanar steel joints

Herein is presented a numerical methodology for a static resistance analysis of symmetrically loaded multiplanar KK joints in circular hollow steel sections. This methodology addresses factors related to the simulation of KK joints such as the material properties, the boundary conditions, mesh generation and refinement, incremental load steps and failure criteria. An objective criterion is proposed to identify the two failure modes most often occurring in KK joints. Failure mode 1 is observed when two neighboring diagonal braces loaded in the same sense act as one brace penetrating the chord together. In the failure mode 2, excessive deformation is observed in the chord region between two neighboring braces, folding the chord wall. However, in some cases the failure mode is not easily identified or both failure types are present. The proposed criterion objectively identifies the failure mode. In order to compute the joint resistance, an important failure criterion often adopted in literature for uniplanar K joints is the one known as Lu’s deformation. In this paper, a strategy is proposed, which is an extension of Lu’s criterion for multiplanar KK joints.

Numerical Modeling of a Composite Hollow Vierendeel-Truss

Composite trusses, a very efficient alternative to overcome large spans for civil engineering, are usually constructed with corner sections, and in many cases, have a central Vierendeel panel, which the main objective is to enable the passage of pipes, unhampered in frames with the presence of diagonals. This work aims to study the feasibility and ultimate limit state to extend Vierendeel panels across the central third of the structure and replace the corner for hollow sections. The fundamental points that supported the theoretical calculation and, especially, how the numerical modeling of the composite Vierendeel-truss was performed, were indicated. The results showed that the regions of the structure with higher stress, determined by finite element method via software Ansys, were the same identified by the analytical calculation and bi-dimensional elastic modeling as acting the highest internal forces, thus validating the methodology of proposed calculation.

Agility based software development for truss design

This article describes the development of an application for structural analysis of tubular trussed girders. Such structural components are widely used on roofs for which long span components are a necessity, e. g., supermarkets, distribution centers, etc. The application supplies hints to the project engineers as to the most economic solutions for a combination of span, loads, and other characteristics. Software development techniques are also explored. Such techniques can be divided into two large groups. In the first one, which is most widely known and used, software development complies with very rigid planning, where processes are more important than skills. This methodology is known as the Rigorous Development System (RDS). The second group, called Agile Development System (ADS), is conceived as an option for those not aligned with the RDS rules. This text describes the experience of an ADS based software development for truss design. In Section 2, the basis of ADS is presented. Section 3 describes the truss design application and civil engineering related concepts. Section 4 brings an example illustrating the application. Conclusions are in Section 5.

Short steel and concrete columns under high temperatures

The growing demand for knowledge about the effect of high temperatures on structures has stimulated increasing research worldwide. This article presents experimental results for short composite steel and concrete columns subjected to high temperatures in ovens with or without an axial compression load, numerically analyzes the temperature distribution in these columns after 30 and 60 minutes and compares them with experimental results. The models consist of concrete-filled tubes of three different thicknesses and two different diameters, and the concrete fill has conventional properties that remained constant for all of the models. The stress-strain behavior of the composite columns was altered after exposure to high temperatures relative to the same columns at room temperature, which was most evident in the 60-minute tests due to the higher temperatures reached. The computational analysis adopted temperature rise curves that were obtained experimentally.