Girder Specimens Research Articles

Experimental study on the behaviours of spliced reinforced concrete girders strengthened with NSM CFRP bars

This paper presents the results of an experimental investigation of spliced and non-spliced reinforced concrete girders strengthened with near surface mounted (NSM) CFRP bars. Six reinforced concrete girder specimens were tested, divided into two groups according to their support condition: simply supported and continuous. Each group thus contained three girders; one girder of each group was single segment without splicing, as a control for comparison purposes. The second girder was spliced in three precast segments without strengthening, and the third girder of each group was spliced in three precast segments strengthened with NSM CFRP bars at the bottom surfaces of the two splice regions. The main variables studied were support conditions, presence of the splicing technique, and strengthening with NSM CFRP bars. The strengthening of spliced girders was achieved by using two bars of 6 mm diameter CFRP in the longitudinal direction. The results for the simply supported group showed that this strengthening resulted to an increase in ultimate load of 11. 25%, as compared with that seen in the spliced girder without strengthening, and of 5.4 % when compared with the control girder. This strengthening method also reduced the maximum deflection by about 23%. The results also showed that strengthening the continuous girder resulted in an increase in ultimate load by 3.76% compared to the spliced girder without strengthening, and the maximum mid-span deflection was reduced by 8.7%. It was also found that the ultimate load of the control girder was greater than that of the strengthened girder by 2.54%. These results indicate that strengthening with NSM CFRP was more effective within the simply supported group than in the continuous group.

Behavioral characteristics of hybrid girders according to type of steel–concrete connection

The design of the reinforcement in the transition zone of hybrid girders (i.e., girders composed of concrete girders and steel girders) in terms of the resistance to the transferred load is critical to ensure the integrity of the structure. Although the availability of various types of reinforcement in the transition zone, existing design guidelines are insufficient with regard to the various reinforcing methodologies. To address this shortcoming, this paper focuses on the behavioral characteristics of hybrid girders with respect to prestressing and three types of connections. Flexural tests were conducted using nine hybrid girder specimens that were designed and fabricated using different combinations of shear studs, anchors, lap joints, and prestressing techniques to achieve the steel-to-concrete connection. A numerical model also is proposed to predict the nonlinear flexural behavior of hybrid girders based on the test results and conventional strain compatibility. The results are used to evaluate the contribution of each component of the connection and derive the combination that best provides resistance for hybrid girders.

Seismic performance comparison of precast segmental bridge girders with different cross sections and boundary conditions under vertical quasi-static cyclic testing: An experimental investigation

In this study, five 1/5-scale bridge girder specimens are tested with vertical quasi-static cyclic loading, in order to understand their performance in high seismic zones. The study is focused on the superstructures at two critical regions: (1) close to mid-span where high moments and low shears are present (2) and close to the supports where high negative moments and high shears are induced. The first case includes one precast segmental bridge box-girder, one precast segmental bridge I-girder, and one reference cast-in-place I-girder, while the second case consists of one precast segmental bridge I-girder and one cast-in-place I-girder. The ratios of the internal and external tendons are 1:1 for case 1 and 3:5 for case 2, respectively. Test results show that cast-in-place girders have better energy dissipation capacity and higher ultimate strength, but the precast segmental girders retain larger displacement capacity and self-centering capability. Internal post-tensioning tendons are subjected to more significant stress concentration at the joint locations of the precast segmental girders, while stress of external tendons is distributed more evenly. In terms of vertical loading, box-girder and I-girder possess similar hysteretic behaviors, as long as the effective widths are the same.

Inelastic moment-rotation response of 690 MPa grade steel I-section girders

Recent specifications have adopted moment-rotation relationships for I-section girders with yield strengths up to 485 MPa to realize adequate and reliable ductility and the development of strength significantly greater than the yield moment. In this study, experiments were performed in order to verify the inelastic moment strength and examine an equation that appropriately expresses the inelastic moment-rotation response of high-strength steel I-section girders in the negative moment region. Three test girder specimens were fabricated and tested to their ultimate bending strengths up to failure. The test results were compared with the maximum strengths predicted for I-girders by finite element analysis and the nominal moment-plastic rotation curve in the specifications. A sufficiently redundant shakedown behavior was revealed by the comparison, which experimentally confirmed the adequacy of the current design equation for the moment-plastic rotation curve to 690 MPa grade steel I-girders. Based on the experimental results, conclusions were drawn regarding the inelastic moment-rotation behavior.

Post‐buckling strength of plate girders subjected to shear – experimental verification

AbstractThis paper describes a calculation method for steel plate girders with transverse web stiffeners subjected to shear. It may be used to predict the failure load or, as a design method, to determine the optimal number of internal web stiffeners. The method is based on the theory of plasticity. Many other theories have been developed, but the method presented here differs from these theories by incorporating the strength of the transverse stiffeners and by assuming that the tensile bands may pass the transverse stiffeners – an effect often observed in tests. Other methods have only dealt with a single web field between two stiffeners.The load‐carrying capacity may be predicted by applying both the lower‐bound and upper‐bound theorems. The upper‐bound solutions show very good correlation with existing tests. The emphasis is placed on the presentation of the tests conducted at the Technical University of Denmark. The test programme comprised six full‐scale plate girder specimens. Agreement between the theory and the tests is very good.

04.06: Post‐buckling strength of plate girders subjected to shear: Experimental verification

ABSTRACTThis paper describes a calculation method for steel plate girders with transverse web stiffeners subjected to shear. It may be used for predicting the failure load or, as a design method, to determine the optimal amount of internal web stiffeners. The method is based on the theory of plasticity. Many other theories have been developed, but the method presented differs from these theories by incorporating the strength of the transverse stiffeners and by the assumption that the tensile bands may pass the transverse stiffeners, which often is observed in tests. Other methods have only dealt with a single web field between two stiffeners.The load‐carrying capacity may be predicted by applying both the lower‐bound theorem and the upper‐bound theorem. The upper‐bound solutions have shown very good correlation with existing tests. The emphasis is attached to the presentation of the tests conducted at the Technical University of Denmark. The test programme contained six full scale plate girder specimens. The agreement between the theory and the tests is very good.

09.06: Continuous fatigue test of welded joint taken from SBHS700 girder specimen

ABSTRACTSteels for bridge high performance structures (SBHS) have high strength, good weldability and workability. SBHS700 of 780MPa class must particularly clarify with respect to fatigue problems. At the previous study, the fatigue test with the SBHS700 girder specimen was carried out and fatigue strength improvement methods to introduce compressive residual stress were used on its out of plane gusset welded joints. However, the previous study did not quantitatively show the fatigue strength improvement because these out of plane gussets have not failed.In this study, in order to clarify the effects of the fatigue strength improvement methods, these out of plane gussets are taken from the girder by gas fusion cutting and made as small fatigue specimens. If there is enough compressive residual stress left at the weld toe, the fatigue tests are carried out.Before the fatigue tests, residual stress at 2mm from treatment edge of centre gusset was measured by the X‐ray diffraction method and compared with previous studies. The target of fatigue test was UIT (Ultrasonic impact treatment). At first, nominal stress range is 100MPa under the same condition of the previous study. If fatigue crack does not appear after 2 million cycles, nominal stress range is increased, such as 150MPa, 180MPa, 200MPa.As a result, enough compressive residual stress was confirmed at the weld toe from the X‐ray diffraction method. UIT specimens reached 2 million cycles in 200MPa stress range. Fatigue test results were considered based on an equation which modified Goodman's diagram applies to the weld toe due to estimate the fatigue limit. Therefore, high fatigue strength can be expected.

Monitoring of tensile force of PSC girder by measuring iron loss variation using EM sensors

The actual tensile force of pre-stressed (PS) tendons of a prestressed concrete (PSC) girder is one of the important factors for evaluating the performance of PSC girder bridges. To measure the tensile force of the PS tendon, this study proposed an iron loss variation based tensile force estimation method using embedded EM sensors. The iron loss of PS tendons are changed according to the applied tensile force. To measure the iron loss of PS tendon of PSC girder, the EM sensor should be embedded in the PSC girder because the PS tendons were located in inside of PSC girder. To verify the proposed method, the experimental tests were performed. The EM sensors were embedded into PSC girder specimen and the iron loss changes due to the variations of tensile forces were measured using EM sensors. According to the measurement results, the proposed method can be a one of the solution to monitor the tensile force of PS tendons.

Behaviour of composite high performance concrete slab on steel I-beams subjected to static hogging moment

This paper investigates the behavior of composite girders made of high performance concrete (HPC) slab connected to steel I-beam through stud shear connectors subjected to hogging moment. Such girders are widely used in bridge construction. However, reinforcing steel bars in the negative moment region contribute significantly to the moment resistance and is found to be ineffective due to cracking of ordinary concrete. This research proposes the use HPCs containing fibers (with better crack resisting and strain hardening characteristics) in the deck slab to enhance both cracking and yield load carrying capacity of such girders at the negative moment region. Four composite girder specimens made of different types of concrete and having variable slab continuity were tested to failure under monotonic loading simulating negative moment. Three types of concrete were employed in the first three girder specimens, namely: Normal Concrete (NC), Steel Fiber-Reinforced Concrete (SFRC) and engineered cementitious composite (ECC). The fourth girder specimen was constructed using two SFRC end slabs connected together with an Ultra-High Performance Fiber-Reinforced Concrete (UHPFRC) closure strip located at the maximum negative moment mid span region. This specimen represents the case of full width -full depth deck slabs resting over steel girders with transverse joints filled with UHPFRC used to accelerate bridge construction. The SFRC and ECC composite girders showed better performance in terms of cracking characteristics (multi-cracking and smaller crack width), higher pre-cracking linear stiffness, higher cracking load, higher concrete strain development during cracking and higher strength compared to their NC counterparts.

Flexural behaviour of a half-decked bulb tee pre-stressed concrete girder: full-scale test and nonlinear finite element analysis

A half-deck bulb tee (HBT) girder, which is an unusual concept for pre-stressed concrete girders, was developed and tested for a long span application. The purpose of the test was to simplify the construction process and increase structural performance by optimising the cross sections and improving the efficiency of the tendon profile. In this study, a full-scale HBT girder, with a length of 60 m and depth of 2.3 m, which includes the .1 m depth of the half-deck, was fabricated and tested to analyse its structural performance. The data observed from the flexural loading tests were evaluated by comparing with the results of finite element analysis (FEA). The tested HBT girder specimen was expected to be sufficiently safe for actual bridge design because it satisfied construction code requirements. The initial cracking load observed during the experiment (1400 kN) was accurately predicted by FEA (1420 kN) and theory (1301 kN). Therefore, the developed HBT girder has sufficient and predictable flexural strength.

Shakedown Behavior of a Continuous Steel Bridge Girder Strengthened With Post-Installed Shear Connectors

An economical method for strengthening non-composite steel girder bridges is to create composite action by “post-installing” shear connectors to engage the steel girder and concrete deck to act as a unit. Concepts of inelastic moment redistribution can be used to further increase the load-carrying capacity of continuous bridges. This paper presents results from experimental testing of a large-scale girder specimen with post-installed shear connectors under large repeated loads leading to moment redistribution at the shakedown limit state.

Experimental and numerical evaluation of a folded plate girder system for short-span bridges – A case study

Bridge owners and engineers focusing on bridge design, management and maintenance continue to search for more efficient ways to design, construct, and maintain their bridge inventory. Recently, a folded plate girder system has been promoted as a cost-effective alternative for the design and construction of bridge superstructures due to merits such as low cost and facilitation of accelerated bridge construction. The folded plate girder system has a structural shape strategically press-brake formed from a single sheet of plate steel and achieves composite action with a concrete deck utilizing shear studs in between. To further facilitate the development and adaptation of the system for bridge application, this paper presents a systematic performance evaluation of the folded plate girder system through experimental and numerical programs. To this end, a folded plated girder specimen was designed, fabricated, and tested to evaluate the constructability and capacity of the girder specimen. Finite Element (FE) Analysis was performed to understand the behavior of the girder specimen under different loading conditions. The predictions using traditional design calculations and FE analysis were compared with the test results. After the FE models were validated against the test data, a full bridge model was established to further investigate the behavior of the bridge under loading condition up to the ultimate load. It was found that the ultimate capacity of the bridge girders were much higher than the bridge demand and the bridge had good ductility until failure. The predictions using the design calculations based on the AASHTO LRFD Bridge Design Specifications were in reasonable agreement with the test results. The FE models showed better predictions since more sophisticated modeling techniques and material constitutive models were used. Results obtained from the sophisticated non-linear bridge model indicated that the girder distribution factors varied along with an increase of the truck loading and especially their change trend was gradually reversed after the yield of the girder steel. And according to the FE results, the distribution factor based on the AASHTO LRFD Bridge Design Specifications was sufficient for the design of the folded plate girder bridge investigated in this study.

Modeling parameters for predicting the postbuckling shear strength of steel plate girders

Bridge fires are becoming an increasing concern, and for steel plate girder bridges in particular, web shear buckling is one of the failure mechanisms that can make it necessary to replace the girder after the fire is extinguished. The objective of this study is to evaluate the web shear buckling response of two experimental plate girder specimens subject to fire conditions, and also to determine how complex computational models must be to accurately characterize the web shear buckling response of steel plate girders subjected to fire. Three parameters are evaluated: boundary conditions representing the flange, representation of thermal gradients, and composite action with the slab. To meet this objective, finite element models with varying parameters are compared to each other and to experimental results. Results show that the presence of a composite slab significantly increases the shear capacity of the plate girder. The presence of thermal gradients makes finite element modeling of the flange more sensitive to the results compared to a uniform temperature distribution. Modeling the girder with a uniform temperature equal to the temperature of the web leads to similar results as modeling with thermal gradients.

Effect of Web Opening on the Ultimate Capacity of Steel Plate Girders under Two Points Load

The structural behavior of steel plate girders with web opening is investigated in this study. An experimental and theoretical investigation of plate girders with circle and square openings in the web was conducted. The experimental work included testing of seven plate girder specimens under two point loads. Three specimens were tested to observe the influence of the circular web opening. The influence of the presence of square web openings was studied by testing other three specimens. The last one was tested without opening as a reference (control) specimen. These specimens had the same dimensions. The experimental results showed that the ultimate load capacity of the girders decreases with increasing the opening size, and the position of plastic hinge depends on the size of hole. Three-dimensional nonlinear finite element analysis has been used to conduct the numerical investigation of the structural behavior of plate girders with web opening. ANSYS (version 12.0) computer program was used in this study. Four- nodes shell element (SHELL 181) was used to represent the steel plate. The proposed finite element model has been used to carry out a parametric study to investigate the effects of two parameters; web slenderness and flange stiffness ratios, on the ultimate load capacity of plate girders with circular web openings.

A Global Integrity Parameter with Acoustic Emission for Load Testing of Prestressed Concrete Girders

Structural evaluation of existing infrastructure has become a critical subject in civil engineering. In recent years, significant efforts have been placed on developing nondestructive techniques such as acoustic emission to monitor and effectively assess the integrity of a structure without causing significant damage. However, acoustic emission methods face challenges regarding the subjectivity of associated performance evaluation criteria and a lack of measurable parameters directly related to the mechanical response of the system. It has been previously suggested that an integrated approach of the cyclic load testing method with acoustic emission techniques may overcome these difficulties and constitute a more effective, nondestructive load testing methodology. The current investigation analyzes experimental data gathered from flexural testing of six full-scale prestressed girder specimens (lightweight and normalweight) and presents a potential approach for damage detection and assessment within the minor to intermediate damage zones based on acoustic emission data.

Connection between Concrete Layers with Different Strengths

As part of a research intending to develop steel-concrete hybrid girder using ultra high performance concrete with compressive strength of 80 MPa, this study conducts loading test on this girder to investigate the methods for its composition with a slab using 30 MPa-concrete and the corresponding interfacial behavior. Prior to the loading test, the design formula of the Eurocode for the shear resistance developed in concrete-to-concrete interface is examined for the interface between concrete layers of different strengths. The effect of the surface roughness on the shear resistance is examined using this formula and finite element analysis to verify the applicability of the formula. Based upon the results, loading test is conducted on girder specimens to evaluate the actual behavior with respect to the interfacial surface condition. The test results reveal that the specimen with rough interface could not develop perfectly composite behavior and experienced adhesive failure. In case of simultaneous action of flexure and shear, it appears that conservative design should be applied without consideration of the interfacial condition when determining the arrangement of shear reinforcement.

FATIGUE TEST OF STEEL GIRDER WEB PENETRATION DETAILS WITH A SLIT

Fatigue cracking in steel girder web penetration details is so dangerous that it can break steel girders. A one-meter-long crack was detected in Yamazoe Bridge in 2006. Since a number of highway bridges with such web penetration details may exist in Japan, it is of urgent importance to understand these fatigue-strength properties. However, few fatigue tests have been reported on steel girder web penetration details. The purpose of this study is to clarify fatigue behavior of steel girder web penetration details with a slit through fatigue tests of specimens with these details. We designed and fabricated girder specimens that have steel girder web penetration details, in which cross-beam bottom flanges are connected to each top or bottom surface of a slit by welding. First, we conducted static loading tests to understand the stress distributions around web penetration details. Second, we conducted fatigue tests to examine fatigue crack initiation and propagation behavior and fatigue strength.

콘크리트 슬래브가 없는 강재주형에서 상하연 온도차에 대한 실측연구

합리적인 온도 설계하중을 연구하기 위하여, 실제 크기의 콘크리트 슬래브가 없는 강상형 거더 교량 시험체를 제작하였다. 높이에 따라 부착된 18개의 온도 게이지에서 5개월 동안 온도 데이터를 측정하였다. 강상형 거더 교량 시험체의 상단과 하단 사이의 온도 차가 계산되고, 온도 구배 모형이 확률 방법으로 제안되었다. 본 연구에서 제시된 모형은 유로 코드에 의해 제안 된 모델과 비교했을 때 약 97%의 상관관계를 보인다. 따라서, 본 연구의 결과로 제안 된 온도 구배 모델은 온도 설계 하중 계산시 기초 자료로 활용 될 수 있다. In order to study the reasonable design thermal loads, the steel box girder bridge specimen which have no concrete slab was manufactured with the real size dimension. The temperature data were measured for 5 month at the 18 thermo gauges which were attached according to height. The temperature differences between the top and bottom flange in steel box girder specimen were calculated and the temperature gradient models were proposed by the probabilistic method. This proposed model showed a correlation of approximately 97% when compared with the similar model of Euro Code. Thus, the temperature gradient models which were suggested in this study may be used as the basis data in calculating the design load temperature.

Effect of holes and segmentation on the structural behavior of a prestressed concrete girder

The developed Holed, Incrementally Prestressed Concrete (H-IPC) girder represents various advanced design concepts. First, the entire self-weight can be considerably reduced by introducing holes in the web, with minimal effect on the moment of inertia. Also, prestress can be efficiently introduced in an incremental way by distributing the anchorages at the holes. The girder can maintain the same sections throughout the span by preventing concentration of the anchorages. This can further reduce self-weight, fabricating time, and cost. Furthermore, the spliced girder system makes it possible to extend the span to more than the conventional length since the segments can be transported and prefabricated on site. The objective of this study is to verify the various advantages of the original design concepts by examining the structural behavior obtained from the loading tests of the 50 m-long full-scale girder specimens. The effect of the holes in the web on overall behavior is one of the main concerns in the test. The test results of a segmented specimen are also compared with those of a non-segmented specimen to investigate the effect of segmentation. It is demonstrated that the segmental H-IPC girder can be effectively used for the design and construction of long-span girder bridges.

Retrofitting for Fatigue Cracks at Connection between the Main Girder Web and Lateral Girder Flange Using the Bolting-Stop-Hole Method with Attached Plates

For the purpose of clarifying the fatigue strength of a main girder web connected to a lateral girder flange which is repaired by bolting-stop-hole method with attached steel plates, fatigue tests have been performed on girder specimens. In addition, fatigue tests have been also carried out on small scale plate specimens modeling the repaired parts in order to investigate the fatigue crack origin and fatigue strength of the repaired parts. Furthermore, the effect of the repair method has been compared with those of stop-hole method and/or bolting-stop-hole method through the fatigue tests. It has been confirmed that the fatigue strength of the repaired parts is considerably high and almost equal to that of friction type of high strength bolted connections.