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

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.

Investigation on partially concrete encased composite beams under hogging moment

2016 ◽  
Vol 20 (3) ◽  
pp. 461-470 ◽  
Author(s):  
Yuchen Jiang ◽  
Xiamin Hu ◽  
Wan Hong ◽  
Mingming Gu ◽  
Weimin Sun
Keyword(s):  
Composite Beam ◽  
Crack Width ◽  
Concrete Slab ◽  
Propagation Speed ◽  
Composite Beams ◽  
Reinforcement Ratio ◽  
Test Results ◽  
Flexural Capacity ◽  
European Code ◽  
Loading Tests

In order to investigate the mechanical behavior of the partially concrete encased composite beam under hogging moment, static loading tests were conducted on one conventional composite beam and three partially concrete encased composite beams. The results show that partially concrete encased composite beams have higher stiffness and flexural capacity under hogging moment as compared with conventional composite beams. It is also found that the concrete encasement is able to enhance the local bucking resistance of the steel beam and effectively reduces the propagation speed of crack width under hogging moment. By comparing different partially concrete encased composite beams, it is indicated that the stiffness and flexural capacity of partially concrete encased composite beams increase with the increase in reinforcement ratio of the concrete slab. Also, with the increase in the reinforcement ratio of the concrete slab, the distribution of cracks on the slab is denser and the propagation speed of crack width reduces. In addition, the calculation methods in both European code and Chinese code can well predict the crack width on the concrete slab, and the ultimate flexural capacity predicted from the simplified plastic theory in Eurocode 4 is in good agreement with test results.

Composite beams under fire loading: numerical modeling of behavior

2016 ◽  
Vol 7 (2) ◽  
pp. 142-157 ◽  
Author(s):  
Kristi L. Selden ◽  
Amit H. Varma
Keyword(s):  
Composite Beam ◽  
Failure Modes ◽  
Concrete Slab ◽  
Material Model ◽  
Composite Beams ◽  
Bottom Flange ◽  
Stress Strain ◽  
Content Type ◽  
Beam Deflections ◽  
Fire Loading

Purpose The purpose of this study was to develop a three-dimensional (3D) finite element modeling (FEM) technique using the commercially available program ABAQUS to predict the thermal and structural behavior of composite beams under fire loading. Design/methodology/approach The model was benchmarked using experimental test data, and it accounts for temperature-dependent material properties, force-slip-temperature relationship for the shear studs and concrete cracking. Findings It was determined that composite beams can be modeled with this sequentially coupled thermal-structural 3D FEM to predict the displacement versus bottom flange temperature response and associated composite beam failure modes, including compression failure in the concrete slab, runaway deflection because of yielding of the steel beam or fracture of the shear studs. Originality/value The Eurocode stress-strain-temperature (σ-ε-T) material model for structural steel and concrete conservatively predict the composite beam deflections at temperatures above 500°C. Models that use the National Institute of Standards and Technology (NIST) stress-strain-temperature (σ-ε-T) material model more closely match the measured deflection response, as compared to the results using the Eurocode model. However, in some cases, the NIST model underestimates the composite beam deflections at temperatures above 500°C.

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

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.

Shear Strength of Void Slab with Polystyrene Forms

2012 ◽  
Vol 217-219 ◽  
pp. 626-629
Author(s):  
Seung Hun Kim
Keyword(s):  
Shear Strength ◽  
Precast Concrete ◽  
Test Results ◽  
Ultimate Shear Strength ◽  
Construction Period ◽  
Failure Patterns ◽  
Shear Performance ◽  
Experimental Works ◽  
Resistance Performance ◽  
Concrete Deck

Void slab systems with polystyrene form and precast concrete deck have been used to reduce the construction period and the self-weight of the slab. This paper presents experimental works on the shear of the void slabs. Four specimens were tested. The main parameters of experiments were the type of polystyrene forms and the thickness of slab. Shear performances of void slabs were evaluated on the basis of failure patterns, load-displacement curves, and ultimate shear strengths. Based on the test results, the unidirectional void slabs had the best shear resistance performance when they used PF2 type of polystyrene forms. For all specimens that failed due to shear, ultimate shear strength was 52% or higher than nominal shear strength by ACI318-08. This indicates that void slabs have a sufficient shear performance in the truss bar arrangement direction

Tests of full-size composite beams with perfobond rib connectors

1995 ◽  
Vol 22 (1) ◽  
pp. 80-92 ◽  
Author(s):  
E. C. Oguejiofor ◽  
M. U. Hosain
Keyword(s):  
Composite Beam ◽  
Concrete Slab ◽  
Composite Beams ◽  
Transverse Reinforcement ◽  
Test Results ◽  
Ultimate Capacity ◽  
Reinforcing Bars ◽  
Flexural Capacity ◽  
Full Size ◽  
Push Out

This paper presents the test results of six full-size composite beam specimens with perfobond rib shear connectors embedded in solid concrete slab. The objective of this investigation was to study the performance of this connector in full-size composite beams and to correlate the test results with those obtained from push-out specimens. In the first three beam specimens, the amount of transverse reinforcement was varied. Two other specimens were used to investigate the effectiveness of more perfobond rib connectors of shorter length. The effect of passing transverse reinforcing bars through the connector rib holes was investigated using the last specimen. Failure of the test specimens was initiated by longitudinal splitting of the concrete slab, eventually culminating in the crushing of concrete in the bearing zone immediately in front of the end perfobond rib connectors. The test results showed that increasing the transverse reinforcement ratio, excluding the wire mesh, from 0.11% to 0.20% led to a 10% increase in the ultimate capacity. The test specimen with six 251 mm long connectors sustained 11% higher ultimate capacity compared to that with four 376 mm long connectors. An increase of 8.4% in the ultimate strength was observed when transverse reinforcing bars were passed through the perfobond rib holes while keeping the total amount of transverse reinforcement unchanged. The experimental values of the ultimate flexural capacity of the beam specimens were, on the average, approximately 1.11 times the predicted values based on push-out test results. Key words: composite beam, perfobond rib connector, push-out test, full-size test, flexural capacity.

Experimental Study on Mechanical Properties of Improved Multi-Grid Composite Wall

2011 ◽  
Vol 217-218 ◽  
pp. 752-757
Author(s):  
Peng Fei Li ◽  
Quan Yuan ◽  
Meng Guo ◽  
Qian Feng Yao
Keyword(s):  
Mechanical Properties ◽  
Point Contact ◽  
Theoretical Research ◽  
Test Results ◽  
Practical Application ◽  
Final Test ◽  
Failure Patterns ◽  
Loading Tests ◽  
Composite Wall ◽  
Hysteretic Characteristics

Two types of improved multi-grid composite wall called point contact multi-grid composite wall and light-steel skeleton multi-grid composite wall were proposed in this paper. In order to study the mechanical properties of improved multi-grid composite wall, the low-cycle reduplicative loading tests of 1/2 scale improved multi-grid composite wall were carried out. Through the analysis of testing phenomenon and final test results, the main failure patterns and failure processes of the walls were summarized, and the mechanical characteristics of improved multi-grid composite wall were discussed, then the seismic performance including bearing capacity, ductility, and hysteretic characteristics were researched. The experimental foundations were provided for the further theoretical research and application of improved multi-grid composite wall in practical application.

Effects of dowels on the mechanical properties of wooden composite beams in ancient timber structures

BioResources ◽  
2021 ◽  
Vol 16 (4) ◽  
pp. 6891-6909
Author(s):  
Xiaoli Han ◽  
Jian Dai ◽  
Wei Qian ◽  
Zhaoyang Zhu ◽  
Baolong Li
Keyword(s):  
Mechanical Properties ◽  
Composite Beam ◽  
Bending Moment ◽  
Composite Beams ◽  
Timber Structures ◽  
Test Results ◽  
Mechanical Behaviors ◽  
Bending Capacity ◽  
Loading Tests ◽  
Failure Conditions

In order to provide more accurate suggestions for the restoration of ancient timber buildings, five types of specimens were designed for static loading tests. The tree species used for the specimens was larch. The wooden composite beams were composed of purlins, tie plates, and fangs. The study analyzed the effects of the number and position of dowels on the mechanical behaviors of wooden composite beams in ancient timber buildings. The bending moment, slippage, strain of the wooden composite beams under the deflection of the beam allowed according to code, and the ultimate bearing capacity of the wooden column composite beams under failure conditions were examined. The test results showed that the dowels could improve the bending capacity of the wooden composite beams. The even distribution of the dowels was beneficial in reducing the sliding effect of the wooden composite beams. Under the amount of deflection allowed by the code, the mid-span section strain along the height of the wooden composite beam approximately conformed to the plane section assumption. The wooden composite beam still had bending capacity after each member failed. The results of this study illustrated that dowels improved the overall mechanical properties of the wooden composite beams.

scholarly journals Prehospital identification of Covid-19: an observational study

2021 ◽  
Vol 29 (1) ◽  
Author(s):  
Douglas Spangler ◽  
Hans Blomberg ◽  
David Smekal
Keyword(s):  
Predictive Value ◽  
Prehospital Care ◽  
The Novel ◽  
Test Results ◽  
Care Providers ◽  
Care Systems ◽  
Primary Hospital ◽  
Novel Coronavirus ◽  
Rule Out ◽  
Descriptive Statistical Analysis

Abstract Background The novel coronavirus disease 2019 (Covid-19) pandemic has affected prehospital care systems across the world, but the prehospital presentation of affected patients and the extent to which prehospital care providers are able to identify them is not well characterized. In this study, we describe the presentation of Covid-19 patients in a Swedish prehospital care system, and asses the predictive value of Covid-19 suspicion as documented by dispatch and ambulance nurses. Methods Data for all patients with dispatch, ambulance, and hospital records between January 1–August 31, 2020 were extracted. A descriptive statistical analysis of patients with and without hospital-confirmed Covid-19 was performed. In a subset of records beginning from April 14, we assessed the sensitivity and specificity of documented Covid-19 suspicion in dispatch and ambulance patient care records. Results A total of 11,894 prehospital records were included, of which 481 had a primary hospital diagnosis code related to-, or positive test results for Covid-19. Covid-19-positive patients had considerably worse outcomes than patients with negative test results, with 30-day mortality rates of 24% vs 11%, but lower levels of prehospital acuity (e.g. emergent transport rates of 14% vs 22%). About half (46%) of Covid-19-positive patients presented to dispatchers with primary complaints typically associated with Covid-19. Six thousand seven hundred seventy-six records were included in the assessment of predictive value. Sensitivity was 76% (95% CI 71–80) and 82% (78–86) for dispatch and ambulance suspicion respectively, while specificities were 86% (85–87) and 78% (77–79). Conclusions While prehospital suspicion was strongly indicative of hospital-confirmed Covid-19, based on the sensitivity identified in this study, prehospital suspicion should not be relied upon as a single factor to rule out the need for isolation precautions. The data provided may be used to develop improved guidelines for identifying Covid-19 patients in the prehospital setting.

Experimental study of moment carrying behavior of typical Tibetan timber beam-column joints

2021 ◽  
pp. 136943322110015
Author(s):  
Ting Guo ◽  
Na Yang ◽  
Huichun Yan ◽  
Fan Bai
Keyword(s):  
Bending Moment ◽  
Structural Performance ◽  
Test Results ◽  
Timber Beam ◽  
Rotational Stiffness ◽  
Trilinear Model ◽  
Column Joint ◽  
Loading Tests ◽  
The Moment ◽  
Relationship Of

This study aimed to investigate the moment carrying behavior of typical Tibetan timber beam-column joints under monotonic vertical static load and also evaluate the influence of length ratio of Gongmu to beam (LRGB) and dowels layout on the structural performance of the joint. Six full-scale specimens were fabricated with same construction but different Gongmu length and dowels position. The moment carrying performance of beam-column joints in terms of failure mode, moment resistance, and rotational stiffness of joints were obtained via monotonic loading tests. Test results indicated that all joints are characterized by compressive failure perpendicular to grain of Ludou. Additionally, it was found that greater LRGB leads to greater initial rotational stiffness and maximum moment of the joint by an increase of restraint length for beam end; however, offsetting dowels toward column resulted smaller stiffness and ultimate bending moment of joints, particularly, offsetting Beam-Gongmu dowels toward column changed the moment-rotation curve pattern of the beam-column joint, accompanied by a hardening stiffness at last phase. Furthermore, a simplified trilinear model was proposed to represent the moment-rotation relationship of the typical Tibetan timber beam-column joint.

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