Stability Behavior of Steel Building Structures in Fire Conditions: Role of Composite Floor System with Shear-Tab Connections

This paper presents a qualitative assessment of the influence of the composite floor system and shear-tab connections on the stability behavior of a typical mid-rise (10-story) steel building subjected to corner compartment fires. A ten-story steel building with composite floor systems was designed following the design practices in the US. The building had an interior core of reinforced concrete (RC) shear walls to resist the lateral loads. Effects of gravity loads and fire conditions were simulated using the finite element method and numerical analysis techniques. The concrete material model used in the numerical simulations was benchmarked using experimental data from concrete slab thermal tests. The results from the numerical investigations indicated that at elevated temperatures, the composite beam undergoes elongation, sagging and rotation at the beam ends. This results in additional rotation and compression demands on the connections at the ends. The shear-tab connections provided significant negative moment resistance at the beam ends at elevated temperatures. This negative moment resistance at the shear-tab connections increased the flexural capacity of the composite beam by effectively redistributing the moment demands due to the applied gravity loads.

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Calculation of Crack Width of Steel-Concrete Composite Beam Prestressed with Internal Tendons

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.889-890.1445 ◽

2014 ◽

Vol 889-890 ◽

pp. 1445-1449

Author(s):

Shuan Jiang ◽

Li Li Bai ◽

Wei Chen Xue

Keyword(s):

Prestressed Concrete ◽

Composite Beam ◽

Crack Width ◽

Concrete Slab ◽

Test Results ◽

Shear Connectors ◽

Slab Width ◽

Current Design ◽

Negative Moment ◽

Average Crack

Steel-concrete composite beam prestressed with internal tendons (SCCPIT) is composed of prestressed concrete slab, steel beam and shear connectors, etc. At present, there is no calculation formula for crack width of SCCPIT in current design codes like European standard Eurocode 4 or American code ASSHTO LERD Bridge Design Specification (2004). In this paper, calculation formulas for crack width of nonprestressed steel-concrete composite beam provided in Code for Design of SteelConcrete Composite Structure (DL/T 50851999) were adopted as a basis for modification. On the basis of available test results, calculation formulas for uneven coefficient of reinforcement strain and average crack space were modified by consideration of concrete slab width and combined force ratio. Hence, empirical calculation formulas for crack width of SCCPIT under negative moment were proposed. In order to verify accuracy of proposed formulas, available test results including results of five simply supported SCCPITs previously conducted by author were introduced, and comparisons indicated that calculated values were in good agreement with test results.

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SHRINKAGE AND CREEP EFFECT ANALYSES OF DOUBLE COMPOSITE CONTINUOUS BOX-GIRDER BRIDGE CONSTRUCTED BY PRE-JACKING METHOD

Proceedings of International Structural Engineering and Construction ◽

10.14455/isec.res.2017.150 ◽

2017 ◽

Vol 4 (1) ◽

Author(s):

Shujin Duan ◽

Bin Wang ◽

Yuanyuan Wang ◽

Runming Niu

Keyword(s):

Composite Beam ◽

Concrete Slab ◽

Bridge Construction ◽

Creep Equation ◽

Box Girder ◽

Concrete Creep ◽

Creep Effect ◽

Shrinkage And Creep ◽

Negative Moment ◽

Girder Bridge

Continuous double steel and concrete composite beam is a new structural system developed on the basis of common steel and concrete composite beam. Controlling concrete slab crack width in a continuous double composite beam is a significant content in the bridge construction process. Jacking-up and landing bearing supports method is applied to a double composite girder bridge construction and its structural mechanical behaviors in the whole process will be simulated. By using of User Programmable Features and ANSYS Parametric Design Language, the commercial FEM software ANSYS was further developed. The exponential model of concrete creep and the implicit solution of concrete creep equation under the action of variable stress were introduced into ANSYS, to realize the concrete shrinkage and creep effect analysis of double composite continuous box-girder bridges constructed by pre-jacking method. The results show that it is improved that the stress state of the top concrete slab in the negative moment regions by pre-jacking method. Due to the effect of concrete creep, the concrete creep will cause tensile stress in the negative moment regions of the composite beam, which will reduce the compressive stress in the top concrete slab. The effect of prestressing is greatly affected by pre-jacking value, and the creep of the concrete also causes the stress redistribution of the concrete and the steel beam.

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Simulation of steel–concrete composite floor system behavior at elevated temperatures via multi-hybrid metaheuristic framework

Engineering With Computers ◽

10.1007/s00366-020-01228-z ◽

2021 ◽

Author(s):

Armin Morasaei ◽

Aria Ghabussi ◽

Soheila Aghlmand ◽

Maziar Yazdani ◽

Shahrizan Baharom ◽

...

Keyword(s):

Elevated Temperatures ◽

System Behavior ◽

Hybrid Metaheuristic ◽

Floor System

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Finite Element Analysis of Composite Ceramic-Concrete Slab Constructions Exposed to Fire

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.861.88 ◽

2016 ◽

Vol 861 ◽

pp. 88-95

Author(s):

Balázs Nagy ◽

Elek Tóth

Keyword(s):

Composite Structures ◽

Elevated Temperatures ◽

Cfd Simulation ◽

Concrete Slab ◽

Composite Ceramic ◽

Reinforced Concrete Beam ◽

Element Analysis ◽

Standard Fire ◽

Using Data ◽

Dynamics Simulations

In this research, conjugated thermal and fluid dynamics simulations are presented on a modern hollow clay slab blocks filled pre-stressed reinforced concrete beam slab construction. The simulation parameters were set from Eurocode standards and calibrated using data from standardized fire tests of the same slab construction. We evaluated the temperature distributions of the slabs under transient conditions against standard fire load. Knowing the temperature distribution against time at certain points of the structure, the loss of load bearing capacity of the structure is definable at elevated temperatures. The results demonstrated that we could pre-establish the thermal behavior of complex composite structures exposed to fire using thermal and CFD simulation tools. Our results and method of fire resistance tests can contribute to fire safety planning of buildings.

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Longitudinal shear capacity of the slabs of composite beams

Canadian Journal of Civil Engineering ◽

10.1139/l76-056 ◽

1976 ◽

Vol 3 (4) ◽

pp. 514-522 ◽

Cited By ~ 1

Author(s):

M. N. El-Ghazzi ◽

H. Robinson ◽

I. A. S. Elkholy

Keyword(s):

Composite Beam ◽

Shear Failure ◽

Concrete Slab ◽

Compressive Force ◽

Longitudinal Shear ◽

Composite Beams ◽

Shear Capacity ◽

Slab Width ◽

Two Parameters ◽

Concrete Elements

The longitudinal shear failure of the slab of composite beams is constrained to occur at a predetermined shear surface. A method for calculating the longitudinal shear capacity of the slab of simply-supported steel–concrete composite beams is presented. The method is based on analyzing the stresses at failure of the concrete elements located at the slab shear surface.A design chart based on estimating the transverse normal stress required within the concrete slab to achieve the full ultimate flexural capacity of the composite beam is proposed. Alternatively, using elastic–plastic stress distribution across the concrete slab, the longitudinal compressive force due to bending and hence the applied moment can be predicted for any longitudinal shear capacity of the slab. The proposed design and analysis when compared to previous tests and analysis showed good agreement.The slab width and the shear span of the composite beam are found to be two important parameters which cannot be neglected when estimating the longitudinal shear capacity of the slab. These two parameters have been neglected in the empirical solutions previously adopted.

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Experimental Study on Mechanical Performance of U-Shaped Steel-Encased Concrete Composite Beam-Girder Joints

Advances in Civil Engineering ◽

10.1155/2021/5580292 ◽

2021 ◽

Vol 2021 ◽

pp. 1-14

Author(s):

Zhangqi Hu ◽

Ran He ◽

Yukui Wang ◽

Weirong Lv ◽

Jingchao Li

Keyword(s):

Composite Beam ◽

Mechanical Performance ◽

Concrete Slab ◽

Bottom Flange ◽

The Novel ◽

Test Results ◽

Construction Period ◽

Failure Patterns ◽

Loading Tests ◽

Two Sides

This paper proposes a novel U-shaped steel-encased concrete composite beam-girder joint (referred to herein as the novel composite beam-girder joint), in which the U-shaped beams at two sides (L and R) are inserted into a shaped sleeve, and the U-shaped girder and two U-shaped beams are connected by the shaped sleeve through welding. Compared with the traditional beam-girder joints, the novel composite beam-girder joints take advantage of easy construction, light weight, and short construction period. The failure patterns, load-strain and load-deflection curves, and strain distributions of the novel composite beam-girder joints were investigated through the static loading tests on two full-scale specimens, denoted as GBJ1 and GBJ2. The two specimens were varied in beam section reinforcements. Specimen GBJ2 was equipped with 3Ф16 additional bars in the U-shaped beams based on Specimen GBJ1. Test results show that the two specimens failed as the through arc cracks developed at the concrete slab interfaces. The additional bars can increase the bearing capacity slightly but will also increase the stress concentration on the bottom flange of the shaped sleeve, leading to the decrease of ductility for Specimen GBJ2. The slab effect is considered in the test and can thus reflect the actual stress state of the beam-girder joints well. This study can provide a reference for the design and application of beam-girder joints.

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Residual shear capacity of cold-formed steel-to-sheathing screwed connections at elevated temperatures

Journal of Structural Fire Engineering ◽

10.1108/jsfe-07-2020-0024 ◽

2021 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Kun Liu ◽

Wei Chen ◽

Jihong Ye ◽

Jian Jiang ◽

Wenwen Chen ◽

...

Keyword(s):

Shear Strength ◽

Elevated Temperatures ◽

Input Parameter ◽

Single Layer ◽

Shear Capacity ◽

Base Layer ◽

Residual Shear Strength ◽

Content Type ◽

Cold Formed Steel ◽

Fire Conditions

Purpose Most previous thermal-mechanical modeling of cold-formed steel (CFS) walls did not consider the failure of screwed connections under fire conditions because of the limited data of such connections at elevated temperatures. Design/methodology/approach In this study, 285 steady-state tests are conducted on CFS screwed connections with single-layer gypsum plasterboard (GPB) and Bolivian magnesium board (BMB) sheathing at ambient and elevated temperatures. The failure of these connections is described as the breaking of the loaded sheathing edge. Findings For the BMB sheathing screwed connections, hydrochloric acid gas is generated and released above 300°C, and the shear strength becomes much less than that of the GPB sheathing screwed connection above 370°C. Hence, BMB may not be suitable for use as the face-layer sheathing of CFS walls but is still recommended to replace GPB as the base-layer sheathing. The major influencing parameters on the shear strength of screwed connections are identified as the type of sheathing material and the loaded sheathing edge distance. Originality/value Based on the previous and present test results, a unified expression for the residual shear strength of screwed connections with GPB and BMB is proposed at ambient and elevated temperatures with acceptable accuracy. It can be used as the basic input parameter of the numerical simulation of the CFS structures under fire conditions.

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Shear tab connection with composite beam subjected to transient-state fire temperatures

Journal of Structural Fire Engineering ◽

10.1108/jsfe-11-2018-0037 ◽

2019 ◽

Vol 10 (4) ◽

pp. 411-434 ◽

Cited By ~ 1

Author(s):

Mohammad Hajjar ◽

Elie Hantouche ◽

Ahmad El Ghor

Keyword(s):

Composite Beam ◽

Transient State ◽

Composite Beams ◽

Slab Thickness ◽

Bottom Flange ◽

Rational Model ◽

Content Type ◽

Geometrical Properties ◽

Axial Forces ◽

Shear Tab

Purpose This study aims to develop a rational model to predict the thermal axial forces developed in shear tab connections with composite beams when subjected to transient-state fire temperatures. Design/methodology/approach Finite element (FE) models are first developed in ABAQUS and validated against experimental data available in the literature. Second, a parametric study is conducted to identify the major parameters that affect the behavior of shear tab connections with composite beams in the fire. This includes beam length, shear tab thickness, shear tab location, concrete slab thickness, setback distance and partial composite action. A design-oriented model is developed to predict the thermal induced axial forces during the heating and cooling phases of a fire event. The model consists of multi-linear springs that can predict the stiffness and strength of each component of the connection with the composite beam. Findings The FE results show that significant thermal axial forces are generated in the composite beam in the fire. This is prominent when the beam bottom flange comes in contact with the column. Fracture at the toe of the welds governs the behavior during the cooling phase in most FE simulations. Also, the rational model is validated against the FE results and is capable of predicting the thermal axial forces developed in shear tab connections with composite beams under different geometrical properties. Originality/value The proposed model can predict the thermal axial force demand and can be used in performance-based approaches in future structural fire engineering applications.

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