J.B. Davison

Rotational stiffness characteristics of steel beam-to-column connections

Abstract A series of tests on a variety of beam-to-column connections suitable for rectangular frames using I-section members has been conducted. The principal objective was the provision of moment-rotation data so that a comparative assessment of the performance of the different types, in terms of connection stiffness and moment capacity, could be undertaken. Thus all tests employed similar beam and column sizes, test apparatus, instrumentation and test procedures. The connections studied were (in ascending order of stiffness and strength): web cleats, flange cleats, combined seating cleat and web cleats, flash end plate and extended end plate. Connections to the column flanges and the column web were included. Major sources of connection flexibility have been identified and the results prepared for subsequent use in assessments of semi-rigid joint action in steel frames.

Experimental and Numerical Investigations of the Behavior of Flush End Plate Connections at Elevated Temperatures

This paper reports on a set of test results on flush end plate connections at ambient and elevated temperatures. The experiments aimed to investigate the behavior of connections at the ends of unprotected beams in fire situations, when they may be subjected to significant tying forces and large rotations at elevated temperatures, as a consequence of high beam deflection. A change in first fracture mode was observed with increasing temperature as the failing component became the bolts rather than the end plate as the strength of bolts reduces faster than that of steel in fire. At elevated temperatures, the use of thicker end plates can enhance the peak resistance, but reduces the rotational capacity of the connection. Finite-element analyses were performed to simulate the tested connections, and gave predictions very close to the observed behavior of the connections in both the loading and the postpeak resistance phases for all the tests at high temperatures. Via these simulations, minor cracks in the end ...

Displacement measurement in studies of steel T-stub connections

Abstract Traditionally steel and composite steel and concrete beam to column joints at the fire limit state are assumed to behave in the same way as used in the design at ambient temperature, that is a joint that is assumed to be pinned at ambient temperature is also assumed to be pinned at elevated temperatures. Recent fire tests on the eight-storey steel frame building at Cardington suggest that joints, which are assumed to be pinned at ambient temperature, can provide significant levels of both strength and stiffness at elevated temperature. In steel structures, the behaviour of joints between beams and columns may be investigated by separate consideration of the various components, which comprise the joint. However, measurement of the distorted profiles of components can be problematic. This paper describes the use of an image acquisition and processing technique for the measurement of deformations in steel T-stub connections, representing the tension component in a steel joint. Although the application has been developed to solve the problems associated with measuring deformations in tests conducted at high temperatures, it also offers advantages over conventional techniques at ambient temperatures.

Modelling of plane composite frames in unpropped construction

Abstract A computer program has been developed to analyse the behaviour of steel-framed buildings with composite floor decks, taking into account both geometric and material non-linearities. In order to simulate the real physical behaviour of a steel-framed building with a composite floor deck the analysis tool has been developed with the capability of predicting the behaviour of two-dimensional sub-frames during both the construction phase and the later composite-beam stage. Partial interaction between the steel beam and the composite slab, the orientation of the profiled metal deck, the effect of additional reinforcement over the support and the semi-rigid nature of the composite beam-to-steel column joint are all included in the analysis. Validation of the computer program against experimental results shows very good agreement not only in terms of load-deflection response but also on load–joint rotation and load-reinforcing bar strains. A description of the mathematical formulation of the four distinct finite elements which have been used in the program is given in Appendix A .

Composite beam behaviour in braced frames

Abstract A numerical study has been conducted to investigate the influence of composite beam-to-steel column joints on the behaviour of composite beams, for a number of subframes representing the spans and loading arrangements of current commercial buildings in the UK. A two-stage analysis has been performed on each of these subframes, varying the steelwork connection, the percentage of reinforcement over the support and the degree of shear connection between the steel beam and the concrete slab. The studies use a computer model which has been developed to simulate the behaviour of steel-framed buildings with composite floor decks. The program is capable of simulating the behaviour of two-dimensional subframes, and considers their two-stage behaviour, both during unpropped construction and as fully composite beams. It is also capable of taking into account the partial interaction between the steel beam and the composite slab, the orientation of the profiled metal deck, the effect of additional reinforcement over supports and the semi-rigid nature of the joint between the composite beam and steel column. In contrast to the usual observations made in isolated joint tests, the study indicates very low values of strains in reinforcing bars at the composite beam-to-steel column joint at the ultimate limit state. The results also indicate that the common types of composite joints available are capable of providing the rotation capacity required to sustain the ultimate load with about 1% of reinforcement over the support, without the use of expensive column web stiffeners.

THE ENVIRONMENTAL IMPACTS OF CONCRETE DESIGN, PROCUREMENT AND ON-SITE USE IN STRUCTURES

Abstract Environmental analyses of materials assume that concrete has only one set of environmental impacts irrespective of the many parameters involved in design and use. This paper presents a more detailed analysis of the environmental impacts of concrete, based on specific calculations configurable down to individual site level. These results indicate the wide range of environmental impacts for each cubic metre of concrete and reveal both that there is a wide range of impacts for different mixes and that there is not always a simple positive correlation between impacts.

High-temperature experiments on joint component behaviour

Publisher Summary The chapter describes the comparison of a series of high-temperature experiments on column webs under transverse compression at different axial load ratios and temperatures with a simplified design approach. The study forms a part of an ongoing project aimed at developing high-temperature models for the behavior of the main components of steel end-plate beam-to-column connections in fire. In this particular phase of the work, the emphasis is on the compression zone in a column web, when transverse compression acts simultaneously with axial compression due to superstructure loading. The main purpose is to construct component-based models of end-plate joints in global numerical modeling of steel and composite building structures in fire conditions. This is the only feasible analytical approach to joint modeling under the simultaneous effects of loading, thermal degradation of materials, and forces due to restraint to thermal expansion.

Effect of lack of fit on connection restraint

Abstract A series of eight tests on different popular types of beam-to-column connection incorporating various forms of lack of fit is reported. The presence of either oversize holes in cleated connections or distortion in end plates has been considered. For the former, additional slip of the bolts permits larger rotations than would occur in equivalent ‘perfect’ connections. The performance of end plate connections appears to be virtually unaffected, even when the bolts have not been tightened sufficiently to remove the gap.

Semi-rigid design of partially restrained columns in non-sway steel frames

Abstract This paper proposes a method for column design in non-sway bare steel structures which takes into account the semi-rigid action of the beam to column connections when estimating the effective length ratio. The simple design method ignores column head moments arising from connection eccentricity for the design of columns in non-sway steel frame. This new method predicts safe column capacities compared with experimental results, analysis and values determined from the UK code BS 5950.

Teaching Architecture and Engineering Students Jointly at Sheffield University

Recently, the departments of Civil and Structural Engineering and Architecture at the University of Sheffield, UK, have introduced modules where architecture students undertake joint project work with structural engineering students. The experience shows that these modules have been successful and proved useful for the students from both departments. Architecture students gain a better understanding of structural efficiency and Engineering students develop a better appreciation of aesthetics and the importance of making the structural system an integral part of the architectural expression. This applies especially to the use of advanced structural systems where the three dimensional geometry of the system can contribute considerably to the quality of the project as a whole.