Composite Frame Systems Research Articles

Experimental research on seismic behavior of a composite RCS frame

To promote greater acceptance and use of composite RCS systems, a two-bay two-story frame specimen with improved composite RCS joint details was tested in the laboratory under reversed cyclic loading. The test revealed superior seismic performance with stable load versus story drift response and excellent deformation capacity for an inter-story drift ratio up to 1/25. It was found that the failure process of the frame meets the strong-column weak-beam criterion. Furthermore, cracking inter-story drift ratio and ultimate inter-story drift ratio both satisfy the limitation prescribed by the design code. Additionally, inter-story drift ratios at yielding and peak load stage provide reference data for Performance-Based Seismic Design (PBSD) approaches for composite RCS frames. An advantage over conventional reinforced concrete and steel moment frame systems is that the displacement ductility coefficient of the RCS frame system is much larger. To conclude, the test results prove that composite RCS frame systems perform satisfactorily under simulated earthquake action, which further validates the reliability of this innovative system. Based on the test result, some suggestions are presented for the design of composite RCS frame systems.

Mathematical Model of Hybrid Precast Gravity Frames for Smart Construction and Engineering

The structural stability, constructability, economic feasibility, environmental-friendliness, and energy efficiency of hybrid composite frame systems have been demonstrated by practical application and research. A hybrid composite frame system combines the economy of precast concrete structures with the constructability of steel frame structures, including erection speed. Novel composite frames will ultimately maximize the efficiency of structural design and facilitate construction. This paper presents hybrid precast frames, which are precast composite frames based on a simple connection between precast concrete columns and beams. The hybrid precast frames designed to resist gravity loading consist of PC columns, PC beams, and steel inserted in the precast members. Steel sections located between the precast columns were simply connected to steel inserted at each end of the precast beams. Dynamic analysis of a 15-story building designed with the proposed composite frame was performed to determine the dynamic characteristics of a building constructed of hybrid frames, including frequencies and mode shapes.

Experimental research and cyclic behavior of buckling-restrained braced composite frame

The pseudo-static tests (PSTs) of one 1/3 scale 2-story 1-bay buckling-restrained braced composite frame (BRBCF) system consisting of concrete-filled circular hollow section (CHS) steel columns, steel beams and BRBs were tested in Harbin Institute of Technology, a same bare composite frame (CF) was tested to compare with BRBCF. The test BRBCF exhibited excellent performance and sustained no strength or stiffness degradation during the significant drift demands imposed by the subsequent quasi-static cyclic test, which possessed good ductility and energy dissipation capacity. Compared with CF system, the stiffness, load-bearing capacity and energy dissipation capacity of BRBCF system increased evidently. The welded splices beam–column-BRB connections are cheap joints and are convenient to install BRBs in construction site, the experiment demonstrated their ability to withstand major ductility demands. The BRBs didn't show global buckling, local buckling and fracture of inner cores. Test also found the damage in beam–column–BRB connections region, including fractures of the gusset and beam welds, local buckling of flanges and webs of beams and enforced loops due to frame and brace action forces, which should be considered in the design of BRBCF. For frames using the proposed gusset connection, the maximum frame drift prior to failure will be governed by the rotational capacity of the beam-to-column connection, not the axial deformation of the BRB. The fracture and buckle of CHS steel tubes at the first story base indicated the thickness of CHS steel tube of composite columns in BRBCF should be enlarged to avoid the early failure of composite columns.

Pseudo-dynamic testing of hybrid frame with steel beams bolted to CFT columns

This paper presents an experimental study on seismic behavior of a composite structural frame system consisting of concrete filled steel tube columns and steel beams with bolted endplate connections. Based on current seismic provisions and previous research, a ten-story prototype building was designed. Analytical models were developed to predict the elasto-plastic behavior of the prototype frame under a series of ground motion records. A four-seventh scale sub-structure model consisting of two stories and one and half span was constructed and subjected to simulated seismic excitations using pseudo-dynamic hybrid testing method. Results from the tests indicate that the model behavior under the simulated seismic loading was consistent with the expected performances analyzed for different earthquake hazard levels. Finally, quasi-static test and pushover test were also conducted to identify the ultimate failure mode of the testing model. The study shows that the proposed system can offer appropriate strength and adequate ductility required for seismic design.

Effect of relative humidity on creep-shrinkage behaviour of composite tall buildings

Relative humidity of environment affects creep and shrinkage behaviour of a concrete member of composite tall buildings. These buildings are more prone to redistribution of forces as adjacent steel columns and RCC shear walls have quite different characteristics. In this paper, study is carried out to evaluate the effect of relative humidity of environment for a composite building using analytical prediction model, CEB-FIP updated 1999 as the facility of short term testing may not be always available and thus, prediction of creep and shrinkage of concrete at any time by extrapolation is not possible. An accurate procedure, Consistent Procedure, CP available in literature is modified by incorporating analytical prediction model CEB-FIP updated 1999. It has been shown that differential deflections in a composite frame shear wall system are significantly affected by relative humidity. It has been further reported that although, the steel columns have only elastic deformation for the chosen composite frame systems, there is significant increase in design forces when relative humidity decreases.

Fiber Beam-Column Model Considering Slab Spatial Composite Effect for Nonlinear Analysis of Composite Frame Systems

AbstractA fiber beam-column model considering the slab spatial composite effect for nonlinear analysis of composite frame systems is proposed and implemented in a general commercial finite element (FE) package. A conventional fiber beam-column model of composite beams is first developed and the computational procedure of this model is presented. A hysteretic law which can consider the strength degradation attributable to repeated reversals of unloading and reloading is proposed to more reasonably and accurately trace the actual complex nonlinear behavior of the concrete material. Furthermore, the formulas for calculating the effective flange widths at two critical limit states are combined with the conventional fiber model so that an improved fiber model, which can reasonably consider the slab spatial composite effect, is realized through the modification of the uniaxial constitutive laws of slab reinforcement and concrete. Finally, the simulations of several tested composite frame structures show that th...

Slab spatial composite effect in composite frame systems. II: Equivalent stiffness and verifications

Based on the research of the companion paper, the influence of the slab spatial composite effect on the lateral stiffness and internal force distributions of composite frame structures has been investigated. The critical factors influencing the equivalent stiffness of composite beams are firstly analyzed using beam-shell mixed element models. Furthermore, a parametric analysis is conducted to derive a simplified design formula of the composite beam stiffness amplification coefficient. The methods for considering the slip effect at the steel–concrete interface have also been discussed. Several regular and irregular composite frame system models with different parameters are used to sufficiently verify the reasonability of the proposed formula in this paper. It can be found that the proposed “line” element composite beam frame model considering the slab spatial composite effect can accurately predict the periods of natural vibration, the seismic story shear forces, the lateral displacements, the story drifts and the internal forces of composite beams etc. However, the model using the formula proposed by Eurocode 4 or neglecting the slab spatial composite effect may give unsatisfactory predictions. Finally, five experimental programs of the composite frames are selected to validate the design methods proposed in this and the companion paper. It can be concluded that the proposed design method in this research can be used to more accurately consider the influence of the slab spatial composite effect in the routine design practice of composite frame systems compared with other methods proposed in the literature and the current design codes.

Slab spatial composite effect in composite frame systems. I: Effective width for ultimate loading capacity

The slab spatial composite effect plays a significant role in the behavior of composite frame structural systems subjected to lateral forces. Since the ultimate loading capacity and stiffness are the two most basic characteristic behaviors in a design practice, this paper focuses on the influence of the slab spatial composite effect on the ultimate loading capacity, and the companion paper pays attention to the structural stiffness and internal force distribution. The extensive verifications of the proposed design methods for evaluating the ultimate loading capacity and stiffness considering the slab spatial composite effect based on various numerical examples and experimental programs are also carried out in the companion paper. In this paper, an elasto-plastic elaborate finite element model of the side joint is firstly developed in order to find the critical factors dominating the slab participation at the ultimate limit states. Furthermore, a parametric analysis is conducted to derive the simplified design formulas of the slab effective widths for calculating the ultimate positive and negative moments at the composite beam end. The predictions calculated using the proposed formulas correlate well with the numerical results. In addition, the proposed design methods are verified adapted for both side and middle joints. Finally, the proposed formulas are compared with some available formulas provided in the literature and current design codes. It is found that the proposed formulas can give the most satisfactory results for predicting the ultimate effective width and beam end moments.

Seismic behavior of CFRSTC composite frames considering slab effects

This paper reports on an experimental and numerical investigation conducted on the seismic behavior of concrete-filled rectangular steel tubular columns (CFRSTC) composite frames. The experimental study was conducted by subjecting two full-scale composite frames to simulated seismic loads. Both frames were composed of CFRSTC and steel beams. One specimen was placed on a reinforce concrete (RC) floor slab and the other was not. The purpose of the test was to investigate the elasto-plastic performance of the CFRSTC composite frame system and to examine the effects of composite action on the behavior of composite frames. The test results showed that the stiffness, strength and energy-dissipating capacity of the CFRSTC frame increased significantly with the presence of the floor slab. Compared with a bare steel beam, the composite beam experienced a decrease in the rotation capacity from 0.046 rad to 0.026 rad. The shear deformation of the panel zone grew because of the composite action, which delayed the fracture of the beam. Finite element (FE) models were established to simulate the tested frames. The results of the FE model fit well with that of the test model in terms of stiffness, strength, hysteretic behavior and component deformation.

Modeling and investigation of elasto-plastic behavior of steel–concrete composite frame systems

This paper presents a mixed finite-element model combining the fibered beam and layered shell elements using the general finite-element program MSC.MARC (2005r2) based on the discussion and comparison of the previous models. The proposed modeling procedure is intended for integrated elasto-plastic analysis of fully connected steel–concrete composite frames subjected to the combined action of gravity and monotonic lateral loads. The model is verified by extensive experiments and examples, and the behavior of composite frames is also investigated intensively. The slab space composite effect and the beam–column semi-rigidity are the two critical factors influencing the structural behavior. These two factors have not been considered simultaneously in some previous models but can be both included in the proposed model. Due to the complex slab space composite effect in composite frames, the previous models with a constant-width effective flange of slab can not trace the actual nonlinear slab behavior, but the proposed model can give accurate results. Since the slip effect between the steel beam and RC slab has negligible influence on the global calculation results of the structural system verified by the calculation examples, the slip effect is neglected in the present study to simplify the modeling procedure and enhance the calculating efficiency. The proposed model possesses good accuracy and broad applicability with simple modeling procedure and high calculation efficiency, and has a great advantage for the large-scale integrated analysis of multistory and high-rise composite frames.

Atlas.txt: exploring linguistic grounding techniques for communicating spatial information to blind users

This paper describes exploratory research into automatically describing geo-referenced information to blind people. The goal is to produce texts giving an overview of the spatial layout, and a central concern of such texts is that they employ an appropriate linguistic reference frame which enables blind hearers to ground the information. The research presented in this paper was based on two hypotheses: (1) directly perceivable reference frames are easier to ground and (2) spatial descriptions drawn from composite reference frame systems composed of more than one reference frame are easier to ground. An experiment exploring text comprehension on a range of texts employing different reference frame systems is presented. The main results indicate that the second hypothesis is supported. A prototype of a natural language generation system, which generates texts describing geo-referenced information from data, is described.

Load Transfer Mechanism of a Hybrid Beam-Column Connection System with Structural Tees

The composite frame system with reinforced concrete column and steel beam can be improved in its structural efficiency by complementing the shortcomings of the two systems. The system, however, has many inherent problems in practical design and construction process due to the dissimilarities of the materials. Considering these circumstance, this research aims for the development of a composite structural system which connects the steel beams to the R/C columns with higher structural safety and economy. Basically, the proposed connection system is composed of four split tees, structural angles reinforced by a stiffener, high strength steel rods, connecting plates and shear plates. Structural tests have been carried out to investigate the moment transfer mechanism 1Tom the beam flange to steel rods or connecting plates through the structural angle reinforced by a stiffener. The four prototype specimens have been tested until the flange of the beam reached a plastic state. The test results indicated that no distinct material dissimilarities between concrete and steel have been detected for the proposed hybrid beam-column connection system and that the stress transfer through the structural angle between the beam flange and steel rods or connecting plates was very encouraging.

A simplified analytical method for unbraced composite frames with semi-rigid connections

The original Muto’s method for the lateral force analysis of conventional unbraced bare steel frames is first modified to incorporate the effects of semi-rigid beam-to-column connections. From which, equations for the calculation of the inter-storey drifts of these frames are formulated using first principles. By comparing the frame analytical results calculated from a rigorous finite element programme, it is shown that the proposed method gives reasonably accurate internal forces and inter-storey drifts estimations of a sway bare steel frame with semi-rigid connections. The proposed modified Muto’s method is then further developed for the manual analysis of unbraced composite frame systems by introducing an improved equivalent beam stiffness to account for the variation of the beam stiffness in the hogging and sagging moment regions. The accuracy of this simplified analytical method is verified by the rigorous finite element analysis of an unbraced composite frame with semi-rigid connections. Last, a parametric study is conducted to quantify the effects of semi-rigid connections on the inter-storey drifts of unbraced composite frames under lateral loads.

Composite floor systems—A mature design option

Abstract The design of composite structures in Canada can be described as being a mature design option. Many aspects of composite structural interaction between steel beams and concrete have been studied and reported in Canada as early as 1922. Since the early 1930s, composite bridges and buildings have been used in this country. Currently, composite steel-concrete floor systems are used in almost all multi-storey steel framed buildings, as well as for floor framing systems in tube-in-tube concrete structures. The purpose of this paper is to focus on those aspects of composite design in Canada which have contributed to the success of the system. Where appropriate, attention is drawn to the research work that has been required to substantiate new and innovative techniques. Designers of composite structures elsewhere in the world may benefit from the lessons which have been learned from the use of this design option in Canada. The features of composite floor framing utilizing composite deck-slabs in multi-storey buildings that have made it economically attractive include access to alternative structural systems, efficiency on longer spans, improved integration of structure with mechanical systems, and superior flatness of floors with minimal deflections under both superimposed dead and live loads. Composite floor framing systems commonly used include conventional beam-girder systems, composite steel trusses and the stub-girder system. Each of these systems is evaluated and discussed, including the concomitant deck-slab system, and slab reinforcing requirements. The quality of structural concrete, especially the shrinkage and creep characteristics that affect either structural performance, serviceability, or both, are noted. The problem areas of composite design and construction are also addressed. These include the tendency for slab cracking over primary support girders and around columns, the need for understanding of beam deflections during construction and control of same by pre-cambering, and particularly, appropriate shoring techniques for stub-girders. It is instructive to look at some examples of comparative costs. Those embodied in this paper include examples of cost savings using composite floor framing compared with conventional non-composite systems.