José Guilherme Santos da Silva

STANDARDIZED COMPOSITE SLAB SYSTEMS FOR BUILDING CONSTRUCTIONS

Abstract The use of steel deck slabs has proved over the years to be one of the most economic structural building systems. Despite this affirmative, mainly for various historic reasons beyond the scope of the present paper, the Brazilian construction industry has not fully exploited the considerable potential of this structural solution. The first part of this paper presents and discusses the analytical and experimental results of a wide-rib composite steel deck developed at the Structural and Materials Laboratory of PUC-Rio. The steel decks results are centred on the steel/concrete longitudinal shear ultimate limit state, load vs. slab strain curve responses and on steel deck design and detailing recommendations. The final part of the paper focuses on an innovative composite slab system made of a steel deck and a styrofoam plate, side by side, filled with reinforced concrete also developed at PUC-Rio. A parametric analysis of the steel deck profile was first performed. When an optimum steel deck profile was established, the investigation proceeded with a series of full-scale-experiments to access the system’s ultimate and serviceability limit states. The experiments also comprised the study of the concrete vs. steel deck interlocking or mechanical shear transfer devices.

Structural analysis of guyed steel telecommunication towers for radio antennas

The usual structural analysis models for telecommunication and transmission steel tower design tend to assume a simple truss behaviour where all the steel connections are considered hinged. Despite this fact, the most commonly used tower geometries possess structural mechanisms that could compromise the assumed structural behaviour. A possible explanation for the structure stability is related to the connections semi-rigid response instead of the initially assumed pinned behaviour. This paper proposes an alternative structural analysis modelling strategy for guyed steel towers design, considering all the actual structural forces and moments, by using three-dimensional beam and truss finite elements. Comparisons of the above mentioned design models with a third alternative, that models the main structure and the bracing system with 3D beam finite elements, are made for three existing guyed steel telecommunication towers (50m, 70m and 90m high). The comparisons are initially based on the towers static and dynamic structural behaviour later to be followed by a linear buckling analysis to determine the influence of the various modelling strategies on the tower stability behaviour. Keywords : telecommunication and transmission towers, guyed steel structures, spatial structures, structural analysis, computational modelling, modal analysis, stability analysis.

Formulação probabilística para análise de tabuleiros de pontes rodoviárias com irregularidades superficiais

An analysis methodology is proposed to evaluate the dynamical effects, displacements and stresses, on highway bridge decks, due to vehicles crossing on the rough pavement surfaces defined by a probabilistic model. To this purpose, the methodology is developed to evaluate the vehicle-structure response under a full probabilistic formulation, running in the frequency domain. The mathematical model assumes a finite element representation of the beam like deck and the vehicle simulation uses concentrated parameters of mass, stiffness and damping. The deck surface roughness is defined by a well known power spectrum density of road pavement profiles. The moving load is formed by an infinite succession of equally spaced vehicles moving with constant velocity. Only steady-state response is considered. Response data are produced on concrete box girder elements assembled as a simple beam. Conclusions are concerned with the fitness of the developed analysis methodology and the mathematical model adequacy.

Fatigue analysis and life prediction of composite highway bridge decks under traffic loading

Steel and composite (steel-concrete) highway bridges are currently subjected to dynamic actions of variable magnitude due to convoy of vehicles crossing on the deck pavement. These dynamic actions can generate the nucleation of fractures or even their propagation on the bridge deck structure. Proper consideration of all of the aspects mentioned pointed our team to develop an analysis methodology with emphasis to evaluate the stresses through a dynamic analysis of highway bridge decks including the action of vehicles. The design codes recommend the application of the curves S-N associated to the Miners damage rule to evaluate the fatigue and service life of steel and composite (steel-concrete) bridges. In this work, the developed computational model adopted the usual mesh refinement techniques present in finite element method simulations implemented in the ANSYS program. The investigated highway bridge is constituted by four longitudinal composite girders and a concrete deck, spanning 40.0m by 13.5m. The analysis methodology and procedures presented in the design codes were applied to evaluate the fatigue of the bridge determining the service life of the structure. The main conclusions of this investigation focused on alerting structural engineers to the possible distortions, associated to the steel and composite bridges service life when subjected to vehicles dynamic actions.

A Stochastic Modelling of the Dynamical Response of Highway Bridge Decks Under Traffic Loads

In this paper an analysis methodology is developed to evaluate the dynamic response, displacements and stresses, on highway bridge decks due to vehicles crossing on the rough pavement surfaces [1]. The analysis methodology follows a statistical model running in the time domain. The mathematical model simulates the bridge structure and the vehicle series as a system, the vehicle-bridge system. The bridge deck follows a straight beam model made discrete by finite elements and nodal concentrated masses, with vertical translations and in-plane rotations as degrees of freedom. Rotatory inertia and shear deformations are not considered. The vehicle simulation uses concentrated parameters of mass, stiffness and damping. Four different types of vehicles are modelled as rigid masses connected by springs and dampers with one, two, four or five degrees of freedom. According to each vehicle model, translational and rotational displacements are considered. The deck surface roughness is defined by a weakly stationary, second order and ergodic random process based on a well-known power spectrum density of road pavement profiles [2]. The moving load is modelled by an infinite series of equal vehicles, regularly spaced, and running at constant velocity. Only steadystate response is considered. Response data are produced on reinforced concrete highway bridge decks made of a straight box girder cross section based on several spans and support arrangements. Results of a parametric analysis are presented to verify the extension of the dynamical effects on highway bridge decks, due to vehicles crossing on the irregular pavement surface. Preliminary results have indicated in all cases studied, in the present investigation, for usual vehicle velocities, that the dynamical effects on highway bridge decks due exclusively to the interaction of the vehicle suspension flexibility with an irregular pavement surface represent a significant parcel on the vehiclebridge system response.

Vibration analysis of orthotropic composite floors for human rhythmic activities

Competitive world market trends have long been forcing structural engineers to develop minimum weight and labour cost solutions. A direct consequence of this design philosophy is a considerable increase in problems related to unwanted floor vibrations. This phenomenon is very frequent in a wide range of structures subjected to dynamical loads. The main objective of this paper is to evaluate an orthotropic solution for composite floors subjected to dynamical actions such as rhythmical activities arising from gymnastics, musical and sports events and ballroom dances. The proposed analysis methodology considers the investigation of the dynamic behaviour of a building floor made with a composite slab system with steel beams and an incorporated steel deck. The results indicated that the investigated composite floor violates the vibration serviceability limit state, but satisfied the human comfort criteria.

Numerical and Experimental Assessment of Stainless and Carbon Bolted Tensioned Members with Staggered Bolts

Current stainless steel design codes, like the Eurocode 3, part 1.4, (2006), are still largely based on analogies with carbon steel structural behavior. The net section rupture represents one of the ultimate limit states usually verified for structural elements submitted to normal tension stress. An investigation aiming to evaluate the tension capacity of carbon and stainless steel bolted structural elements was performed and in this article, the results are discussed and compared in terms of stress distribution, and force-displacement curves, among others. The result assessment was done by comparisons to the Eurocode 3 (2003) provisions for carbon and stainless steels. The investigation indicated that when stainless steel is used in certain structural engineering applications like joints under tension forces, the current design criteria based on deformation limits need to be re-evaluated, especially due to the differences in the yields for ultimate deformation and stress ratios.

Vibration Analysis of Long Span Joist Floors Submitted to Human Rhythmic Activities

In the last years, building structures are more and more becoming the modern landmarks of urban areas. Designers seem to continuously move the safety border, in order to increase slenderness and lightness of their structural systems. However, more and more steel and composite floors (steel-concrete) are carried out as light weight structures with low frequencies and low damping. These facts have generated very slender composite floors, sensitive to dynamic excitation, and consequently changed the serviceability and ultimate limit states associated to their design. The increasing incidence of building vibration problems due to human rhythmic activities led to a specific design criterion for rhythmic excitations to be addressed in structural design (Allen et al. 1985); (Almeida, 2008); (Almeida et al., 2008); (Bachmann & Ammann, 1987); (Faisca, 2003); (Ji & Ellis, 1994); (Langer, 2009); (Murray et al., 2003); (Silva et al., 2008). This was the main motivation for the development of a design methodology centred on the structural system dynamical response submitted to dynamic loads due to human activities. This paper investigated the dynamic behaviour of composite floors (steel-concrete) subjected to the human rhythmic activities. The dynamic loads were obtained through experimental tests conducted with individuals carrying out rhythmic and non-rhythmic activities such as stimulated and non-stimulated jumping and aerobics (Faisca, 2003). The description of the loads generated by human activities is not a simple task. The individual characteristics in which each individual perform the same activity and the existence of external excitation are relevant factors when the dynamic action is defined. Numerous investigations were made aiming to establish parameters to describe such dynamic loads (Allen et al. 1985); (Bachmann & Ammann, 1987); (Faisca, 2003); (Murray et al., 2003). The present investigation considered the dynamic loads, based on results achieved through a long series of experimental tests made with individuals carrying out rhythmic and nonrhythmic activities. This investigation described these dynamic loads, generated by human activities, such as jumps with and without stimulation, aerobics, soccer, rock concert audiences and dancing (Faisca, 2003).

Um sistema de laje mista para edificações residenciais usando perfis de chapa dobrada com corrugações

The composite steel-concrete system has been used in various major projects motivating the development of an efficient composite floor system using cold-formed steel sections with web corrugations. The system was based on previous investigations that involved the development of steel deck prototypes using various types of interlocking mechanisms in the concrete to steel deck interface. An ideal section evaluation was made to determine an efficient steel profile that presented a good mechanical adherence to the concrete interface while keeping a ductile behavior. Variables like weight, height, thickness and yield stress amongst others were investigated. An experimental program consisting of a full-scale composite slab test was executed to validate the proposed composite cold-formed system.

Non-Linear Dynamical Response of Steel Portal Frames with Semi-Rigid Connections

Traditionally, the steel portal frame design assumes that beam-to-column joints are rigid or pinned. Rigid joints, where no relative rotations occur between the connected members, transfer not only substantial bending moments, but also shear and axial forces. Alternatively, pinned joints are characterised by an almost free rotation movement between the connected elements preventing the bending moment transmission. Despite these facts, it is largely recognised that the great majority of joints does not exhibit such idealised behaviour. These joints, called semi-rigid, should be designed according to their actual structural behaviour. Considering all these facts one of the main objectives of this investigation is to propose a modelling strategy to represent the dynamical behaviour of semirigid joints under dynamic actions. The developed finite element model included geometric nonlinearities and considered the influence of non-linear and hysteretic joint stiffness. The updated Lagrangean formulation is used to model the geometric non-linearity. The mathematical model calibration was made based on comparisons to semi-rigid tests and other numerical models [1],[2] and proving to be in accordance to them. However, it must be emphasized that cautions should be taken on the direct use of the results in structural design. The main reasons for this affirmative are related to the occurrence of very important distortions due to the consideration of the semi-rigid joints geometric non-linearity effects on the steel portal frames dynamical response.