On the Limit Behaviour of Moment Resisting Connections Under Uncertainties

Moment resisting connections are mainly designed to transfer bending moments and shear forces. Generally speaking, the design strength of a moment resisting connection can be classified as full-strength (moment capacity of the connection equal to or greater than that of the connected member) or partial-strength (the moment capacity of the connection less than that of the connected member). Similar remarks can be made regarding the stiffness defining connection rigid or semi-rigid if compared to the stiffness of the connected member. In the past, full-strength connections have been widely adopted especially in moment resisting frames and their structural performance relied on the proper behaviour of welding. However, the research following the 1994 Northridge and 1995 Kobe earthquakes demonstrated the lower than expected performance of welded connections, stimulating the onset and development of pre-qualified connections to be adopted especially in seismic areas. Among these connections the most studied ones are those belonging to the Reduced Beam Section (RBS) typology, being the so-called “dogbone” connection the most adopted. The dogbone presents a bending strength and a flexural stiffness lesser than the ones of the original structural member. Recently, the authors proposed a special device suitably designed to realize an innovative moment resisting connection for steel beam elements belonging to the RBS typology. Such a device, called Limited Resistance Plastic Device (LRPD), is constituted by three different portions: the central one is devoted to the onset and development of plastic deformations and presents geometrical dimensions reduced with respect to those of the original structural member; the external ones are devoted to recover the stiffness of beam-device system to that of the original structural member and present greater geometrical dimensions. This latter remark allows to affirm that, from a connectivity point of view, the stiffness of LRPD at the column-beam interface, is greater than the one of the original structural member. Another fundamental remark is that the structural connections are intrinsically characterized by uncertainties related either to geometrical or to material ones. Usually, the effect of uncertainties is covered by the use of safety coefficients and the analyses are performed referring only to the nominal values of the geometrical and mechanical characteristics. However, in order to perform a more complete interpretation of the mechanical behaviour of the studied connections, a non-deterministic analysis approach can be used. Aim of the paper is the characterization of the structural behaviour of the referenced connections (“dogbone” and LRPD) taking into account the main geometrical uncertainties and that related to the material strength by performing suitably Monte Carlo simulations and by determining the relevant M-N domains. Starting from the described characterization, different commercial steel profiles will be considered in order to build a series of M-N domains useful to quantify the safety level and the range of usability of the two different RBS approaches. Finally, the implemented applications will lead to demonstrate the greater reliability of LRPD compared to the classical dogbone.

A STUDY OF COLLAPSE SUSCEPTIBILITY AND RESISTANCE OF LOADED CABLE-SUPPORTED PIPE STRUCTURE SUBJECT TO A SUDDEN BREAK OF CABLE MEMBER

Cable-supported pipe system (CSPS) provides a suitable system of structure for meeting the stringent structural requirements of pipeline bridges. However, due to a composite action of cable with truss and pipe members, the sudden failure of its structural member may lead to undesired vibratory response and collapse. The occurrence of a sudden break of the CSPS structural member is characterized by spontaneous dynamics and internal force rearrangement. The present study aims to investigate parametrically the collapse susceptibility and resistance of scaled down CSPS model in the event of a sudden break of the cable member by combined experimental and numerical procedures. The displacement of the structure, the pattern of internal force rearrangement, and dynamic responses were comparatively evaluated. Experimental results depict imminent cable failure under load and attendant dynamic response, but without a total collapse of the CSPS structure. Critical members causing large dynamic response amplitudes were identified and the mitigation of collapse was evaluated. Dynamic increasing factor (DIF) methods was utilized for the evaluation of the dynamic response of the sudden cable break resulting from the pattern of responses between the cable members and the rest of the CSPS structure. Comparison with provisions in other studies shows higher values DIF of the CSPS cable members which led to proposed evaluation using dynamic factor (DF). Thus, the dynamic factors for the sudden break of various cable members along the span and the errors were also estimated considering the parametric of design variables which will enable easy utilization during the structural process of CSPS.

Case Study on Prediction of Temperature in Compartment Considering Fire Conditions in Buildings

Current fire resistance standards for major structural members of buildings require uniform fire resistance performance (in hours). However, buildings may be vulnerable to various local-fire conditions, depending on the industry or business, so it is necessary to examine their differences through simulations. In this study, the existing room corner test (KSF ISO 9705) and simulation results were compared to verify the reliability of the simulations. Next, the similarity of the results was identified. Simulations of actual buildings were performed based on local-fire conditions, and it was verified that the temperature varies by location. Based on the results, it is necessary to focus on performance-based fire resistance design rather than the specification-based design, which requires uniform fire resistance performance in hours. Simulation case studies should be conducted to reflect the diversity of the fire and structural member conditions.

Study on Self-Sensing Performance of Graphene-Modified FRP Bars

At present, the distributed long-gauge optical sensor on fiber reinforced polymer(FRP) bar cannot be manufactured through integrated production. On the other hand, the point-sensing technology of the self-sensing bar will cause deviations in structural health monitoring (SHM). To solve these issues, applying the graphene/epoxy on FRP members is a feasible method for the piezoresistive characteristics of graphene. In this paper, basalt FRP (BFRP) bars with graphene/epoxy film were tested under static tensile load and the resistance was measured at the same time until they were broken down. The results suggested that the changing rate of resistance was linearly correlated to the strain. This fact indicated that the graphene-modified BFRP bar can well reflect the stress condition of the structural member within a safe range.

Design and Analysis of Earthquake Resistant Building (Three Storeyed R.C.C. School Building) using STAAD.PRO

The field of Earthquake Engineering has existed in our country for over 35 years now. Indian earthquake engineers have made significant contributions to the seismic safety of several important structures in the country. However, as the recent earthquakes have shown, the performance of normal structures during past Indian earthquakes has been less satisfactory. This is mainly due to the lack of awareness amongst most practising engineers of the special provisions that need to be followed in earthquake resistant design and thereafter in construction. In India, the multi-storied building is constructed due to high cost and scarcity of land. In order to utilize maximum land area, builders and architects generally proposed asymmetrical plan configuration. These asymmetrical plan buildings, which are constructed in seismic prone areas, are likely to be damaged during earthquake. Earthquake is a natural phenomenon which can be generate the most destructive forces on structure. Buildings should be made Safe for lives by proper design and detailing of structural member in order to have a ductile form of failure. The concept of earthquake resistant design is that the building should be designed to resist the forces, which arises due to Design Basic Earthquake, with only minor damages and the forces which arises due to Maximum Considered Earthquake, with some accepted structural damages but no collapse. This paper studies the Earthquake Resisting Building.

Investigating strut and tie model in deep beams

The Strut-and-Tie model (STM) approach evolves as one of the most useful design methods for shear critical structures and for other disturbed regions in concrete structures. The model provides a rational approach by representing a complex structural member with an appropriate simplified truss model. The literature review showed that there is no single unique STM for most design situations encountered. This report summarizes the STM approach and related research as well as the results of linear and nonlinear analysis of a deep beam using SAP2000 and ABAQUS Software.

Performance Of UPHC Filled Steel Column

Ever since the development of the Ultra-High-Performance Concrete [UHPC], research has been going on in the use of hollow steel tubes filled with UHPC as a super-frame structural member. The key area of this research is to study the influence of confinement effect on the behavior of the Super-frame column and to develop guidelines in modern codes for the design of such composite sections. This project report compares the performance UHPC filled steel tubes and conventional sections using a computer program, Lab experiment and analytical analysis. The results of all the analysis show that UHPC filled tubes perform better than the conventional sections such as only steel sections or concrete sections. Additionally, Eurocode - 4 predicts reasonable results.

Performance Of UPHC Filled Steel Column

Ever since the development of the Ultra-High-Performance Concrete [UHPC], research has been going on in the use of hollow steel tubes filled with UHPC as a super-frame structural member. The key area of this research is to study the influence of confinement effect on the behavior of the Super-frame column and to develop guidelines in modern codes for the design of such composite sections. This project report compares the performance UHPC filled steel tubes and conventional sections using a computer program, Lab experiment and analytical analysis. The results of all the analysis show that UHPC filled tubes perform better than the conventional sections such as only steel sections or concrete sections. Additionally, Eurocode - 4 predicts reasonable results.