Zhongcheng Ma

Transversely corrugated cold‐formed steel (CFS) arch elements are widely used as self‐supporting building roofs. The transverse corrugations and the unusual cross‐section shapes complicate the design of such members under compressive loading. Since the current Eurocode does not cover the design rules for CFS arches with transverse corrugations, the objective of this study is to develop a method for determining the effective cross‐section of such members under compression load. In total 36 stiffness tests and 27 compression tests were carried out on the corrugated CFS arches with different thicknesses and curvatures. Steel arch profiles with thickness of 1.5 mm has 55% higher ultimate load value than the profiles with 1.1 mm thickness due to a bigger effective area to resist the axial compressive forces. The smaller the steel arch radius is, the more susceptible it is to buckle and stability failure due to the eccentricity of compression load along the curvature. The stiffness is dir...

Abstract Shot nailed connections are widely used in roof constructions to fasten cold-formed steel sheeting to supporting trusses. At ambient temperatures, neither EN 1993-1-8 nor EN 1993-1-3 can be used directly for this type of connection. Besides, no design guidelines are available in EN 1993-1-2 for designing the same type of connection in fire. In this paper, with the verified Finite Element (FE) models and procedures, three major failure modes under lap shear loads, such as bearing failure, shear-out failure and net-section failure, are investigated. In addition, the material bearing failures, the effects from out-of-plane curling of thin sheet and the contribution from frictions between the connected parts are analyzed at both ambient and elevated temperatures. Further, parametric analyses are conducted to investigate the effects of the end distance, the edge distance and the protuberance height on the connection resistance. After that, the design resistance functions for bolted connections given in EN 1993-1-8 are revised for designing shot nailed connections. Finally, the design resistance functions are calibrated using First Order Reliability Method (FORM) and the partial safety factor is derived.

In recent years, increasing interest has been shown throughout Europe in developing and designing slim floor systems in steel-framed buildings. This paper presents the fire resistance behavior of the composite asymmetric slim floor beam as an isolated member and as a part of the frame using numerical analysis methods. Three schemes were investigated, including isolated beams, a plane subframe with semirigid beam-to-column connections, and a 3D slim floor frame system. The first scheme aimed to explore the fire resistance of the beams according to standard fire-testing methodology. The objective of the second scheme was to reveal the effect of frame continuity on the fire resistance of the slim floor beam and the mechanical interaction between the frame elements. The third scheme was to preliminarily identify the influence of the composite slab on the beam behavior in fire. The investigations show that the isolated slim floor beam has a 60-min standard fire resistance without any additional fire protection, if the load ratio is <0.5. As a part of the frame, the beam still keeps its stability even when the temperature of the bottom steel flange of the beam reaches up to 900 7C (90- min ISO fire exposure). The analyzed results indicate that the axial restraints provided by the surrounding parts cause a larger deformation of the beam in the earlier ISO heating phase and a more stable behavior thereafter. The rotational restraints essentially cause the change in the applied load ratio in fire, which can be quantified using the ''modified load ratio'' proposed in this paper.

A parametric temperature–time curve for structural fire design purposes is developed for small and medium compartment fires. This method may be used, with reasonable precision, to estimate the temperature history of a fully developed compartment fire. It concerns mainly ...

Abstract There is an increasing interest in the steel-concrete composite slim floor construction in the Nordic Countries and the UK. The slim floor beams, which are partly contained within the floor slab, have inherent good performance under fire. At the moment, a new type of slim floor beam is under development in Finland. In this paper, the thermal and structural performance of this new slim floor beam is investigated under fire by using numerical analysis programs. The temperature analysis and calculations of the load-bearing capacity are carried out under fire conditions (both ISO standard fire and natural fire) according to Eurocode 1 Part 2.2. The structural fire resistance behaviour of this new slim floor beam is investigated and the relationship between the fire resistance time and load ratio under ISO standard fire is discussed. Moreover, the minimum load ratio of the beam under a natural fire is analyzed. The critical relationship between the minimum load ratio and the fire parameters (opening factor and fire load density) is also established, provided that the structural failure is caused by a reduction in the flexural capacity of the fire-exposed beam.

A structural fire safety design method for composite steel-concrete slim floor structures was developed, including the characterization of fully-developed compartment fire curves and the equivalent fire exposure, temperature analysis of the composite structures, and the structural response analysis of composite slim floor structures subjected to fire. Special interest was given to the structural responses of the slim floor beam both as an isolated member and a part of the frame structure. The mechanical interaction behind the global deformation response of the frame was emphasized. Although the analyzed objects concentrated on composite slim floor structures, the according fire safety design method and the explored structural response mechanism in fire are equally applicable to other types of building structures.

In recent years, increasing interest has been shown throughout Europe in developing and designing slim floor systems in steel-framed buildings. This paper presents the fire resistance behavior of the composite asymmetric slim floor beam as an isolated member and as a part of the frame using numerical analysis methods. Three schemes were investigated, including isolated beams, a plane subframe with semirigid beam-to-column connections, and a 3D slim floor frame system. The first scheme aimed to explore the fire resistance of the beams according to standard fire-testing methodology. The objective of the second scheme was to reveal the effect of frame continuity on the fire resistance of the slim floor beam and the mechanical interaction between the frame elements. The third scheme was to preliminarily identify the influence of the composite slab on the beam behavior in fire. The investigations show that the isolated slim floor beam has a 60-min standard fire resistance without any additional fire protection, if the load ratio is <0.5. As a part of the frame, the beam still keeps its stability even when the temperature of the bottom steel flange of the beam reaches up to 900 7C (90- min ISO fire exposure). The analyzed results indicate that the axial restraints provided by the surrounding parts cause a larger deformation of the beam in the earlier ISO heating phase and a more stable behavior thereafter. The rotational restraints essentially cause the change in the applied load ratio in fire, which can be quantified using the ''modified load ratio'' proposed in this paper.

Abstract There is an increasing interest in the steel-concrete composite slim floor construction in the Nordic Countries and the UK. The slim floor beams, which are partly contained within the floor slab, have inherent good performance under fire. At the moment, a new type of slim floor beam is under development in Finland. In this paper, the thermal and structural performance of this new slim floor beam is investigated under fire by using numerical analysis programs. The temperature analysis and calculations of the load-bearing capacity are carried out under fire conditions (both ISO standard fire and natural fire) according to Eurocode 1 Part 2.2. The structural fire resistance behaviour of this new slim floor beam is investigated and the relationship between the fire resistance time and load ratio under ISO standard fire is discussed. Moreover, the minimum load ratio of the beam under a natural fire is analyzed. The critical relationship between the minimum load ratio and the fire parameters (opening factor and fire load density) is also established, provided that the structural failure is caused by a reduction in the flexural capacity of the fire-exposed beam.

Abstract Shot nailed connections are widely used in roof constructions to fasten cold-formed steel sheeting to supporting trusses. At ambient temperatures, neither EN 1993-1-8 nor EN 1993-1-3 can be used directly for this type of connection. Besides, no design guidelines are available in EN 1993-1-2 for designing the same type of connection in fire. In this paper, with the verified Finite Element (FE) models and procedures, three major failure modes under lap shear loads, such as bearing failure, shear-out failure and net-section failure, are investigated. In addition, the material bearing failures, the effects from out-of-plane curling of thin sheet and the contribution from frictions between the connected parts are analyzed at both ambient and elevated temperatures. Further, parametric analyses are conducted to investigate the effects of the end distance, the edge distance and the protuberance height on the connection resistance. After that, the design resistance functions for bolted connections given in EN 1993-1-8 are revised for designing shot nailed connections. Finally, the design resistance functions are calibrated using First Order Reliability Method (FORM) and the partial safety factor is derived.

In recent years, increasing interest has been shown throughout Europe in developing and designing slim floor systems in steel-framed buildings. This paper presents the fire resistance behaviour of the composite asymmetric slim floor beam as an isolated member and as a part of the frame using numerical analysis methods. Three schemes were investigated, including isolated beams, a plane subframe with semi-rigid beam-to-column connections and a three-dimensional slim-floor frame system. The first scheme aimed to explore the fire resistance of the beams according to standard fire-testing methodology. The objective of the second scheme was to reveal the effect of frame continuity on the fire resistance of the slim floor beam and the mechanical interaction between the frame elements. The third scheme was to preliminarily identify the influence of the composite slab on the beam behaviour in fire. The investigations show that the isolated slim floor beam has a 60-minute standard fire resist...

When design steel structures, structural fire safety design is equally important as loading-bearing design. Currently, structural fire design is moving from prescriptive approach to performance-based approach. One of the key essential techniques for performance-based approach is the numerical analysis technique of steel structures in fire using advanced calculation models. In this paper, the structural fire analysis procedure from 2D temperature analysis to structural response using Ls-Dyna was developed and validated by the fire tests of a simply supported beam, a simple steel frame and a both axially and rotationally restrained steel column. 2D implicit temperature analysis is efficient in these cases and sufficient accuracy was achieved. Using explicit solver, structural response in fire can be simulated up to collapse with the considerations of the temperature-dependent material non-linearity and possible contacts in joints. Both beam element models and shell element models were...

Two different types of finite element models to simulate the steel columns supported by sandwich panels are developed in this paper and validated by the full-scale tests by Hedman-Petursson (2001) at ambient temperature. The bracing forces in self-drilling screws, the effect of connections in horizontal joints, effects of the lateral stiffness of self-drilling screws are studied using the developed FE models. Effect of different configurations of loading eccentricity on the buckling resistances of steel columns supported by sandwich panels are further analyzed in this paper.

A parametric temperature–time curve for structural fire design purposes is developed for small and medium compartment fires. This method may be used, with reasonable precision, to estimate the temperature history of a fully developed compartment fire. It concerns mainly ...