Full-scale Destructive Tests Research Articles

Flexural load-rating of slab-on-girder bridges by nonlinear proxy finite-element analysis

ABSTRACT The proxy finite-element analysis (PFEA) technique is significantly extended to improve its utility and its predictions of bridge ultimate capacity are verified. Refinements and extensions to the method include a substantial reduction in up-front computational effort, explicit consideration of the effects of skewness on bridge behavior, and expansion of the technique’s mechanics formulation to include the effects of prestressing. PFEA’s prediction of ultimate flexural capacity is verified by simulating the capacity of a previously conducted, full-scale destructive test of a prestressed concrete girder bridge with good prediction of recorded load-deflection data. Live-load testing (LLT) of five, skewed, reinforced concrete bridges is described. The tested bridges are then load-rated by PFEA, leading to average increase in rating factor exceeding 120%, as compared with an average increase of 34.9% with LLT. This demonstrates that PFEA’s consideration of material nonlinearity leads to larger increases in predicted capacity while retaining the conservative assumptions required by design and analysis codes. Practical usage and implementation of PFEA are addressed, including application to ratings and permitting.

Full-scale experimental and numerical investigation on the ductility, plastic redistribution, and redundancy of deteriorated concrete bridges

Due to structural degradation, the performance of concrete bridges may degrade with time and result in catastrophic consequences. A novel approach is developed for evaluating the time-variant reliability of multi-girder concrete bridges considering the effects of the load-carrying mechanism and redundancy. By considering three failure modes at both the component and system levels, a new performance indicator is proposed for quantitatively evaluating the load elastic distribution and plastic redistribution among multiple girders. The adverse effects of material deterioration on the structural capacity, ductility, redundancy, load-carrying capacity, and failure mechanism are also investigated and incorporated into the analytical procedure, in which an incremental nonlinear finite element analysis of a 3D fiber beam element is used. Furthermore, the results associated with full-scale destructive tests of two in situ deteriorated bridges, a reinforced concrete (RC) and a prestressed RC (PRC) T-girder bridge, are adopted to evaluate the accuracy of the proposed approach. The feasibility and satisfactory performance of the proposed framework are evaluated using these two real-world bridges. The results demonstrate that the load-carrying mechanism and redundancy significantly affect the structural ultimate load-carrying capacity and time-variant reliability of deteriorating structures.

Flexural Behavior of a 30-Meter Full-Scale Simply Supported Prestressed Concrete Box Girder

Compared with scaled-model testing, full-scale destructive testing is more reliable since the test has no size effect and can truly record the mechanical performance of the structure. However, due to the high cost, only very few full-scale destructive tests have been conducted on the flexural behavior of prestressed concrete (PC) box girders with girders removed from decommissioned bridges. Moreover, related destructive testing on the flexural behavior of a new precast box girder has been rarely reported. To investigate the flexural behavior and optimize the design, destructive testing of a 30-meter full-scale simply supported prestressed box girder was conducted at the construction site. It is illustrated that the failure mode of the tested girder was fracture of the prestressing tendon, and the corresponding maximum compressive strain in the top flange was only 1456 μ ε , which is far less than the ultimate compressive strain (3300 μ ε ). Therefore, the concrete in the top flange was not fully utilized. A nonlinear analysis procedure was performed using the finite strip method (FSM). The validity of the analysis was demonstrated by comparing the analytical results with those of the full-scale test in the field and a scaled model test in a laboratory. Using the developed numerical method, parametric analyses of the ratio of reinforcement were carried out. The prestressing tendon of the tested girder was increased from four strands to six strands in each duct. After the optimization of the prestressed reinforcement, the girder was ductile and the bearing capacity could be increased by 44.3%.

Falling-object protective structure for tractors in service: Prototype design and validation

A falling-object protective structure (FOPS) is a safety device fitted to self-propelled agricultural vehicle that provides reasonable protection for the operator in the driving position against accidental falling objects. To be certified, a FOPS undergoes a standardised full-scale destructive test to prove its resistance to falling objects. This destructive test procedure is expensive and unsuitable for custom-made FOPS manufactured individually. In the case of a tractor in service, for which manufacturers do not offer a FOPS device, there is no certified method to evaluate the performance of a custom-designed FOPS, other than this destructive procedure. The work described in this paper, funded by the French Agriculture Ministry, proposes a design and a validation of a cantilever FOPS to equip tractors that have two-post rear roll-over protective structures (ROPS). The main requirement of the custom-designed FOPS is to meet the performance and protection level of certified structures. A design approach with the goal of achieving optimal design was adopted. At each stage, design alternatives are compared qualitatively and quantitatively, using numerical simulation, to assist decision making. A validation method based on mathematical modelling and full-scale tests, according to standardised test conditions, was adopted. This validation process made it possible to approve the design choices and to determine the scope of validity of the proposed FOPS.

Destructive and minor destructive tests on masonry buildings: Experimental results and comparison between shear failure criteria

In this paper, an extensive experimental campaign conducted on existing masonry buildings is presented. The main objective of this activity was to study the shear behaviour of masonries constituted by clay bricks and lime-based mortar evaluating the most suitable techniques applicable to get reliable information on the material mechanical properties. Minor destructive tests (MDT) and destructive tests (DT) were performed on eight masonry buildings, damaged by the 2012 Emilia earthquake (Italy). The tests results are here presented and discussed, focusing on the strength parameters obtainable from each test type and on the definition of appropriate failure domains. The strength predictions are finally compared with the outcomes of full-scale destructive tests.

In-Situ Destructive Testing of Ancient Strengthened Masonry Vaults

ABSTRCTDeveloping suitable tools to assess the actual structural performance and designing and executing interventions to improve that performance is a key issue in the field of conservation and enhancement of architectural heritage. This article presents the results of five full-scale destructive tests performed on the Castello di San Pietro in Verona (North-East Italy), a building set on a hill above the city and going back to the 19th century under the Habsburg Empire. It evaluates the behavior of the barrel vaults of 5.6 m span, 1.1 m rise, and 27 cm thickness in the original building. Although experimental work is common in the relevant literature, the testing program described here was not performed on reconstructed vaults but on original elements, which can reveal their real behavior more clearly. Four strengthening solutions were also evaluated, in which organic and inorganic fibers were applied to both types of matrix.

Experimental and analytical behavior of a prestressed U-shaped girder bridge

This paper presents an experimental and analytical investigation on the behavior of a U-shaped girder subjected to operation, cracking and ultimate loads. A full-scale destructive test was conducted on a U-shaped girder to study the cracking process, load-carrying capacity, failure mechanism and load-deformation relationships. Accordingly, the tested U-shaped girder was modeled using ANSYS and a non-linear element analysis was conducted. The investigation shows that the U-shaped girder meets the specified requirements of vertical stiffness, cracking and ultimate load capacity. Unfavorable torsional effect is tolerable during operation. However, compared with box girders, the U-shaped girder has a more transverse mechanical effect and longitudinal cracks are apt to occur in the bottom slab.

Field and Theoretical Analysis on the Response of Destructive Pile Subjected to Tension Load

Most field tests are carried out using working piles for verification purposes in China, and loading tests are terminated before achieving true pile capacity. In this work, two full-scale destructive loading tests on tension piles instrumented with strain gauges were conducted to capture true pile capacity. The load-displacement response, load transfer, and threshold of the pile-soil relative displacement for fully mobilizing skin resistance in the uplift case were discussed. It was found that the shaft resistance degradation is observed to be along the pile depth with a reduction factor of 0.905 to 0.931, and the thresholds of pile-soil relative displacement for fully mobilizing skin resistance of the tension pile in different soils are found to be in the range 0.67% to 1.34% of the pile diameter. Based on the field test results, a simple softening model was proposed to describe the degradation behavior of skin friction along the pile-soil interface. Further study was conducted to assess the influence of the threshold of pile-soil relative displacement for fully mobilizing skin friction and the reduction factor on the skin friction. As to the analysis of the response of single pile subjected to tension load, a highly effective iterative computer program was developed using the proposed skin friction softening model. Comparisons of the load-settlement response for the well-instrumented tests were given to demonstrate the effectiveness and accuracy of the proposed simple method.

Destructive field tests on mobilization of end resistance of cast-in-situ bored piles

A series of well-designed full-scale destructive load tests were conducted on six bored piles to investigate the influence of loose debris at the pile tip on end resistance. The results show that soft debris below the pile tip will weaken the mobilization of end resistance. The ultimate tip resistance of post-grouted pile is 2.05 times that of the pile without post-grouting and the ultimate tip resistance in the second load cycle is 2.31 times that of pile in the first load cycle. The relationship between unit end resistance and displacement follows a linear model and a bilinear mode in the first load cycle and the second load cycle, respectively, whereas the unit end resistance-displacement response of post-grouted bored pile can be simulated using a bilinear mode. The critical end resistance ranges between 2 000 kN and 3 000 kN and the critical displacement ranges between 2.5 mm and 4.5 mm in the bilinear mode. As for piles rested on moderately-weathered peliticsiltstone, the socketed length has no effect on the end resistance because of the existence of loose debris.

Analysis on Response of Destructive Piles with and without Post-Grouting Craftwork

Two full-scale destructive load tests were conducted on test piles to capture the response of post-grouted and non-post grouted piles. The results show that the relationship between end resistance and displacement developed at the pile base follows a linear model for the piles without and with post-grouting craftwork. It is observed that the limiting total skin friction of pile after post-grouting craftwork is 1.067 times that of non-post grouted pile, whereas the ultimate tip resistance of post-grouted pile is about 1.113 times that of the pile without post-grouting craftwork. At the ultimate loading level, the pile compression has been found to be 45.7% to 50.3% of the pile head settlement. For the long post-grouted pile, the pile shaft compression should be taken into account and enhancement of the shaft strength can reduce the pile head settlement.

Dynamic Characteristics of an Overpass Bridge in a Full-Scale Destructive Test

Verification of vibration-based damage detection through a full-scale actual structural testing is an important learning opportunity. From such a test, the evolution of dynamic characteristics can be observed, damage detection methods can be validated, and baseline criteria for typical structural damage can be formulated. This paper describes a case study on a full-scale destructive testing of an overpass reinforced concrete bridge. Damage is introduced by cutting one of the bridge piers at the footing level allowing vertical settlement. This type of damage is expected to simulate the condition in which a bridge suffers from nonuniform pier settlement or hidden damage inside piles of buried foundations. By applying time and frequency domain vibration analysis, as well as a system identification technique, changes in dynamic characteristics caused by the damage are evaluated. The results clearly indicate the changes in frequencies as an indicator of damage presence, while the change in mode shapes can be used to locate the damage. The paper also discusses the application of the damage detection method based on outlier analysis of the autospectra function using the bridge ambient acceleration responses. The results indicate that the presence of damage at an early stage can be detected by observing the outliers in multivariate data, and the detection accuracy improved when damage has significantly changed the dynamic characteristics of the structure.

Vibration Characteristics of an Overpass Bridge During Full-Scale Destructive Testing

Progressive destructive testing is a schematic way of applying damage on a structure and evaluating the immediate effects in terms of the change in structural characteristics. Generally a progressive destructive test is conducted on a small scale specimen in a controlled environment such as laboratory. On-site full-scale progressive damage of an existing structure, which is rare considering cost and size of the structure, is an important learning opportunity in a framework of structural health monitoring research. Such a test provides an opportunity to observe the real change in structural characteristics which often masked by environment effects. Moreover such a test can be utilized as a benchmark for several damage detection methods. In this paper a full-scale progressive destructive test of an overpass post-tensioned bridge is presented. The bridge was instrumented with vibration sensors and the ambient acceleration responses were recorded during damage stages. Damage was introduced by cutting one of bridge piers at the footing level. This type of damage is expected to simulate a condition where a bridge suffers from a non-uniform pier settlement. By applying time and frequency domain vibration analysis, as well as system identification, evolution of dynamic characteristics caused by the damage is quantified. The results show that changes of natural frequencies are clearly visible, thus can be used as indicator of damage presence, while the change in mode shapes can be used as the local damage indicator.

Slip between Glue-Laminated Beams in Stress-Laminated Timber Bridges: Finite-Element Model and Full-Scale Destructive Test

Stress-laminated timber bridge decks consist of several sawn timber beams or glue-laminated (glulam) beams held together with prestressed steel bars. Frictional shear stresses between the beams transfer loads between individual beams. Because the vertical (transverse) shear stress component has been extensively discussed, this paper considers the horizontal shear stress. A full-scale test and corresponding finite element simulations for a specific load case confirmed that horizontal slip occurred between beams. Using an elastic-plastic material model, the finite element model handled both vertical and horizontal frictional slip. The results showed that the finite element model gives reliable results and that slip in general leads to permanent deformations, which may increase with load cycling. Horizontal slip between beams over a large area of the bridge deck begins at a low load, resulting in a redistribution of load between beams, but does not lead to immediate failure. Vertical slip between beams starts at a high load close to the load application point and leads to failure.

Full-Scale Destructive Bridge Test Allows Prediction of Ultimate Capacity

Contemporary bridge design is generally based on designing individual members for the maximum force effect that each member may experience. This approach ignores the system-level interactions of these individual members, which may greatly increase the ultimate strength of the complete structure. In an attempt to understand better the load redistribution mechanisms that lead to this increase in ultimate strength, the destructive testing of a skewed steel I-girder bridge was planned and executed. However, because of the enormous system-level reserve capacity of the structure, the structure generally responded elastically, despite being loaded with the equivalent of 17 HS-20 design vehicles. Thus, a validated finite element analysis (FEA) approach was used to predict the ultimate capacity of this structure and to analyze the force redistribution as the bridge's elastic limit was exceeded. The FEA results predicted that the equivalent of 41 HS-20 vehicles was needed to plastify fully the four girders of the subject bridge and show the significant amount of yielding that occurs in the cross-frames when the ultimate capacity of the girders is achieved.

Development of devices and methods for simulation of hurricane winds in a full-scale testing facility

The International Hurricane Research Center (IHRC) at Florida International University (FIU) is pursuing research to better understand hurricane-induced effects on residential buildings and other structures through full-scale aerodynamic and destructive testing. The full-scale 6-fan Wall of Wind (WoW) testing apparatus, measuring 4.9 m tall by 7.3 m wide, is capable of generating hurricane-force winds. To achieve windstorm simulation capabilities it is necessary to reproduce mean and turbulence characteristics of hurricane wind flows. Without devices and methods developed to achieve target wind flows, the full-scale WoW simulations were found to be unsatisfactory. To develop such devices and methods efficiently, a small-scale (1:8) model of the WoW was built, for which simulation devices were easier and faster to install and change, and running costs were greatly reduced. The application of such devices, and the use of quasiperiodic fluctuating waveforms to run the WoW fan engines, were found to greatly influence and improve the turbulence characteristics of the 1:8 scale WoW flow. Reasonable reproductions of wind flows with specified characteristics were then achieved by applying to the full-scale WoW the devices and methods found to be effective for the 1:8 scale WoW model.

Destructive Testing under Simulated Hurricane Effects to Promote Hazard Mitigation

The human and financial toll of hurricanes on U.S. east and gulf coast communities has been immense. The International Hurricane Research Center at Florida International University focuses on a first-of-its-kind full-scale destructive testing method that can lead to understanding of hurricane-structure interaction and development of effective mitigation measures. Analogous to the effective study of the failure modes during crash testing, significantly enhancing automobile safety, and performance analysis through shake-table testing to improve seismic resistance of buildings, hurricane engineering research will improve building resiliency through full-scale destructive testing, and raise the public’s awareness of the need to improve building safety and of the means to achieve this goal. This paper describes the full-scale destructive testing concept, details applications through pilot tests, illustrates the scientific approach underlying the current testing method, and discusses future plans to develop innovative techniques to mitigate hurricane destruction. This research is a necessary condition for available and affordable insurance, which is paramount to sustain the economy of the U.S. coastal states.

Performance of a Rollover Protective Structure for a Bulldozer

Rollover protective structures (ROPS) are safety devices fitted to heavy vehicles to provide protection to the operator during an accidental rollover. At present, ROPS design standards require full-scale destructive testing, which can be expensive, time consuming, and unsuitable for small companies. More economical analytical methods would require an understanding on postyield behavior and energy absorption capacity of ROPS. With this in mind, this paper treats a bulldozer ROPS using experimental and analytical techniques to generate research information that will enable development of analytical design guidance and enhance safety.

Wall of Wind Full-Scale Destructive Testing of Coastal Houses and Hurricane Damage Mitigation

Damages during extreme wind events highlight the weaknesses inherent in coastal residential building construction and underscore the need for improving the structural performance of typical residential buildings. Also, there is a tremendous concern for the existing stock of buildings that are not sufficiently designed and constructed to an acceptable building code. Conducting research to better understand simultaneous hurricane-induced wind, rain, and debris effects on the built environment will lead to innovative design technologies that can mitigate hurricane wind damage. The International Hurricane Research Center (IHRC) at the Florida International University (FIU) has developed a new research approach to better understand categories 1 to 5 hurricane-induced effects on residential buildings and other structures through full-scale, destructive testing, much the same way that the automobile industry tackled the crash worthiness issue or the earthquake community approached building safety. This research will foster the development of novel mitigation techniques to improve our built environment's resilience to hurricane impact. To develop these advanced techniques, we will subject test models of representative building structures or appropriate portions of such structures to hurricane-induced wind–rain–debris effects in a controlled and repeatable environment using the Wall of Wind testing apparatus developed by the IHRC. Through such full-scale destructive testing, performance-based evaluation, and failure-mode analysis, innovative mitigation techniques will be developed. Wall of Wind experimentation has the potential for revolutionizing our building and retrofitting practices.

Out-of-plane flexural behavior of unreinforced red brick walls strengthened with FRP composites

This paper presents the results of a study focused on evaluating the out-of-plane flexural behavior of two fiber reinforced polymer (FRP) composite systems for strengthening unreinforced red brick masonry walls. The full-scale tests followed the International Code Council Evaluation Service (ICC-ES) AC 125 procedure. In the experimental program, a total of four full-scale destructive tests were conducted on UMR red brick walls. One wall specimen was used as control (as-built) specimen without composites, and the remaining three wall specimens were strengthened with either E-glass/epoxy or carbon/epoxy composite systems with different fiber architecture. The effect of applying a cross-ply laminate on the ultimate failure mode has been investigated. Full-scale experimental results confirmed the effectiveness of the FRP composite strengthening systems in upgrading the out-of-plane flexural structural performance of URM walls. In addition, an analytical model was developed to predict the ultimate load capacity of the retrofitted walls. The analytical modeling is based on deformation compatibility and force equilibrium using simple section analysis procedure. A good agreement between the experimental and theoretical results was obtained.

Elastoplastic large deformation analysis of a lattice steel tower structure and comparison with full-scale tests

The objective of this paper is to develop a numerical model for simulating ultimate behavior of lattice steel tower structures. We present the elastoplastic large deformation analysis of a lattice steel tower structure using finite element analysis and we compare the numerical results with full-scale destructive tests. A 2-node three-dimensional L-section beam finite element proposed in our previous work is used. The beam finite element can consider eccentricities of loading and boundary conditions as well as material and geometrical nonlinearities. We model a real tower structure section using the beam elements and perform a nonlinear static analysis to obtain the limit behavior of the tower in two different load cases. The numerical results are discussed in detail.