Full-scale Experimental Investigation Research Articles

Waterproofing performance of longitudinal segmental tunnel joints under external loads: a full-scale experimental investigation

Waterproofing performance of longitudinal segmental tunnel joints under external loads: a full-scale experimental investigation

Full-scale experimental investigation of wind loading on ballasted photovoltaic arrays mounted on flat roofs

Ballasted photovoltaic (PV) systems, in comparison to roof-anchored systems, are gaining notable popularity on commercial flat roofs due to the benefits they provide in evading roof penetration and the associated insulation issues. However, the accurate estimation of the aerodynamic uplift forces and their consequent effects on system responses presents a new design challenge. Moreover, possible dynamic effects, characterized by wind induced vibrations, are not accounted for in the design of PV systems in ASCE 7–22, potentially rendering the code design coefficients unconservative. Additionally, the available literature is based on roof anchored PV systems, while experiments in the literature utilizing ballasted PV systems which have distinct behavior and dynamic properties are very limited. The current study aims for a better evaluation of the behavior of ballasted PV systems and the mitigation efficiency of wind deflectors under simulated extreme wind events. To fill this knowledge gap, a 2 x 2 full-scale ballasted PV array model, equipped with wind deflectors and located on a model flat roofed structure was tested at the Wall of Wind (WOW) Experimental Facility (EF). The experimental campaign consisted of aerodynamic and dynamic tests, which permits pressure measurements on the panels under high Reynolds number flow, realistically influenced by the vibrations of the deflectors, as well as capturing of array's dynamic characteristics. The results show that wind deflectors effectively reduce both net area-averaged and point pressure coefficients, particularly under cornering wind directions. While the top surface pressures remained unchanged with the addition of deflectors, the bottom surface pressures experienced a substantial decrease, and the power spectral densities of pressure fluctuations were significantly reduced. Wind deflectors also proved to be efficient in reducing the correlation of instantaneous aerodynamic pressures occurring at different points, reducing the area-averaged peak pressures on the panels and, consequently, reducing net uplift on the entire array. Moreover, the aerodynamic loads were amplified by up to 30% due to dynamic effects caused by the wind induced vibration of the panels. Finally, from the failure assessment tests, a cascading failure mode was observed where the supports are consequently lifted before the entire system is flipped.

Experimental Investigations on Structural Behaviour of Reusable Interlocking Steel column base Connection with Demountability

Implementing a circular economy in construction is one of the potential approaches to limit the natural resource consumption by the construction industry and construction waste generation after demolition. There exist necessities for constructing buildings with easier demountability and direct reusability. One of the key aspects of reuse is designing with structural connections for demountability after service life, rendering the buildings for reuse. Therefore, this study endeavours to develop a directly reusable interlocking hold-down type column base connection for steel structures through full-scale experimental and theoretical investigations. The new reusable column base connection consists of a connector plate to replace the anchor rods in the traditional exposed column base connections to connect the concrete footing with the steel column and base plate assembly. This paper investigates the structural behaviour of the new reusable column base connection subjected to monotonic lateral loading and determines the effective embedment depth required for the connector to avoid concrete failure. A loading protocol that signifies reuse through repeated loading sequences is adopted for this study. Thus, each specimen is loaded for three repeated reuse cycles. A theoretical method based on the traditional component model concept representing the connection components as a combination of spring assembly is developed to predict the initial elastic stiffness of the connection. This will consequently aid in estimating the lateral displacement occurring for the corresponding design load. The theoretically predicted stiffness values are in good correlation with the experimental results. The design example for stiffness calculation is also provided for industrial practical applicability.

A full-scale experimental investigation of natural gas explosion in a 710-m long utility tunnel with multiple pipelines

Natural gas poses significant risks to the safe operation of utility tunnels, which house multiple critical infrastructure systems, including natural gas pipelines. To date, no full-scale gas explosion tests in utility tunnels have been published, and there is ongoing debate about whether pipelines can withstand such explosions. This study presents the first-ever 1:1-scale experiments conducted in a 710-meter-long tunnel with cross-sectional dimensions of 3.2 m × 2.6 m. Three pipelines, each approximately 25 m in length and constructed to industrial standards, were used to investigate potential damage. The experiments comprehensively captured the development of flow fields, including flame images, flame signals, temperature, and overpressure, as well as pipeline responses. Results revealed that variations in overpressure within the combustion region were driven by both positive and negative feedback loops. A significant pressure drop was also observed as airflow passed through a local expansion. The experiments further demonstrated that while pipelines within utility tunnels are unlikely to be directly damaged by gas explosions, accessories such as racks are at high risk of severe destruction. These findings offer essential insights for improving the safety design, construct, and operation of tunnel-like spaces involving flammable gases.

Full-scale experimental investigation of prestressed concrete bridge girders strengthened with aluminium channels

The bridge network in South Carolina encompasses more than 9,000 structures, many of which were originally constructed to accommodate H10 (89 kN) or H15 (134 kN) truck loads and thus require strengthening to carry current loading standard (HL-93). The South Carolina Department of Transportation (SCDOT) has recognized that prestressed concrete channel bridge girders, a specific type of bridge superstructure, often face challenges in achieving adequate load ratings, based on flexural strength. Hence, it is imperative to explore strengthening methods for these girders. Aluminium alloys possess desirable properties that make them attractive as external reinforcement materials. While previous studies have investigated the use of aluminium alloys on small-scale reinforced concrete members, there is a lack of investigation on their use on full-scale prestressed concrete bridge girders. To address this gap, this study investigates the feasibility of utilizing aluminium alloy channels as an external reinforcement material on full-scale prestressed concrete channel bridge girders. The main goal of this paper is to propose a strengthening method for prestressed concrete channel girders that is cost effective and easily implemented in the field to reduce the number of load-posted bridges in the state of South Carolina. Nine girders from recently decommissioned bridges in South Carolina were tested under flexural loading conditions to failure. The test program consisted of six unstrengthened girders, one strengthened with bonded aluminium channels (SE), one strengthened with bonded and bolted aluminium channels (SEB), and one strengthened with bolted aluminium channels (SB). Before testing, a visual inspection of the girders was conducted to identify any existing deterioration, and each girder was given a condition rating based on the Specifications for the National Bridge Inventory (SNBI). Theflexuralicate that externally anchored aluminium alloy channels with bolts was the most effective strengthening method in terms of practicality and increase in the flexural strength. Moreover, the results also revealed that the measured flexural strength of the girders varied based on the extent of the observed girder deterioration.

Cross-ties with linear hysteretic damping for cable vibration mitigation: Theoretical analysis and full-scale experiment

This study investigates cross-ties with linear hysteretic damping (HDCs) for vibration mitigation of stay cables through theoretical analysis and full-scale experiments. The formed cable networks are modeled by considering cables as taut strings and the HDCs as mass-less elements of complex stiffness. Frequency equation of the system is formulated analytically and is solved numerically. Then, the influence of HDCs on system dynamics is discussed for typical cable networks and considering HDCs realized by a rigid tie in series with high damping rubber. The results indicate that the HDCs can realize high damping for multiple modes because of the frequency independency of hysteretic damping and no restriction on the installation location. Increasing the loss factor of the cross-tie is significant for improving system damping, but less effective for system frequency modification. Extending HDCs to the ground and using multiple HDCs are effective in further enhancing multi-mode frequency and damping of the system. Furthermore, full-scale experimental validations and investigations are conducted based on three cables of approximately 40 m. Experimental results have validated the effectiveness of HDC in enhancing system damping. This study demonstrates that the easily implementable HDCs have excellent performance in vibration mitigation of multi-mode cable vibrations.

Full-scale experimental investigation into stability of segment-SCC-steel tube lining under external pressure

To investigate the mechanical deformation characteristics of the ‘Segment-SCC-Steel Tube’ combined bearing lining structure under internal and external pressure, the loading device and monitoring system for the stability analysis of the full-scale lining were proposed. The effect of cracked encased concrete and local external pressure on the instability mode of thin-walled steel pipes was explored by full-scale model experiment and three-dimensional FEM numerical simulation. The influence of SCC (Self-Compacting Concrete) and stiffening rings on the stability of steel pipes subjected to external pressure was discussed. The results show that SCC cracks occur and intensify with increasing internal pressure. The external water acts directly on the steel tube through cracking, resulting in wavy deformation, and the gap between the SCC and steel tube further increases. When calculating the critical external pressure for the steel pipe, the constraint of encased concrete can be ignored, and only the constraint effect of the stiffening ring can be considered. Therefore, the Von Mises formula was used to predict the critical external pressure between the stiffening rings with high accuracy. In addition, the stiffening ring can mitigate the crack propagation of nearby SCC. The steel tube remained in the elastic stage under internal pressure. In the full-scale experiment, the external pressure could not continue to rise after reaching 0.65 MPa. Nevertheless, the amplitude of the buckling wave continued to increase. It is considered that the steel pipe is in an unstable state, and the failure mode is dominated by single-lobe buckling.

The MD study of water short-range order during liquid-liquid transition: Toward the second critical point

Full-scale thermodynamic experimental investigations of the liquid-liquid transition and different water phases remain challenging due to spontaneous crystallization and the complexity of studies on the nanosecond time scale. Moreover, the specific position of the second critical point in water is still unclear. This study used molecular dynamics to reproduce the structural properties of both low- and high-density waters and to characterize changes in the order parameters, average number of hydrogen bonds, and ordering of neighboring molecules during liquid-liquid transitions and in regimes of supercooled waters. A rapid change in calculated parameters under increased pressure could be attributed to a first-order phase transition. In addition, we provided evidence that low-density water becomes dissolved in high-density water inclusions as the temperature or pressure increases. The presumed location of the second critical point has been identified as TC ≈ 220 K, PC ≈ 1.5 kbar, and ρC ≈ 1.02 g/cm3.

Full-scale experimental investigation on the performance of seamless asphalt plug joint through mixture design and structural enhancements

The seamless asphalt plug expansion joint integrates a traditional asphalt plug joint (APJ) with an overlying continuous asphalt concrete layer, preventing block failure of the asphalt plug joint and enhancing driving comfort. However, typical damages such as fatigue cracking, rutting, and permanent deformation often occur in the upper asphalt layer. This is attributed to the inadequate stiffness of the lower joint plug mastic, particularly under high temperatures and heavy loads. To extend the service life of asphalt plug expansion joints under such conditions and enhance their durability, efforts were made to bolster the performance of the lower asphalt plug joint mixture and improve anti-rutting performance. This study involved: (1) Qualifying APJ mixture requirements under high temperature and heavy load by focusing on two critical material properties: good rutting resistance and permanent deformation resistance. High temperature rheological properties of these binders were examined through temperature scanning tests and multi-stress creep recovery tests (MSCR). (2) Exploring the impact of binder-aggregate ratios and specimen molding methods (standard compaction, paving vibration and pre-mixing) on the bonding strength and rutting resistance of the APJ mixture. This analysis was conducted using pull-off tests and dynamic stability tests. (3) Development of a novel APJ featuring dowel bars to enhance vertical deflection resistance and joint horizontal movement. Comprehensive laboratory tests showcased the modified joint structure's resilience after numerous test cycles, demonstrating exceptional resistance to bending and vertical deformation. The significant findings from this research provide valuable insights for optimal material selection, appropriate joint design, and installation guidelines for seamless asphalt plug expansion joints.

Fatigue behaviour of root crack in stiffener-to-deck plate weld at crossbeam of orthotropic bridge decks

Steel Orthotropic Bridge Decks (OBDs) are widely used in long-span and movable bridges. Fatigue resistance analysis plays an important role in the design or assessment of OBDs. One possible fatigue failure is the crack initiating from the weld root of stiffener-to-deck plate connections at crossbeams. A full-scale experimental investigation in this study using a 20 mm thick deck plate with a dimension of 9.4 m × 5.1 m, including three crossbeams, represents the modern designed OBDs. The experiments show an arrest of crack propagation with a final crack depth of approximately 75% of the deck plate thickness. On the contrary, through thickness cracks develop in deck plates of 10 or 12 mm. Hot spot stress based fatigue detail categories (DC) using various failure criteria derived from the tests. Analysis with the effective notch stress shows that the DC has low sensitivity to the amount of weld penetration. The results of analyses with the eXtended Finite Element Method (XFEM), employed to analyse the fatigue crack propagation path and crack arrest, are in line with the experimental study.

Full-Scale Experimental and Field Investigations into Expansion Mechanism of Foamed Polyurethane and its Lifting Behaviors for Repair and Maintenance of Railway Slab Track Systems.

Excessive settlement of the subgrade seriously reduces the service quality of slab tracks and threatens trains' running safety. While the utilization of foamed polyurethane is recognized as an effective solution, previous research on its expansion mechanism and its impact on track lifting requires further refinement. Accordingly, a series of full-scale tests, including expansion force tests on foamed polyurethane with diverse qualities and lifting tests of polyurethane grouting with varied qualities on the track structure, have been conducted. The expansion development process of foamed polyurethane is meticulously elucidated, and key expansion parameters are analyzed. Simultaneously, this research explores the lifting behavior of foamed polyurethane grouting under the slab tracks, yielding new insights into essential lifting parameters for track formation repair and maintenance. Based on the experimental data, this study proposes new empirical formulas to comprehensively describe both the expansion mechanism of foam polyurethane and its lifting behavior under the slab tracks. The outcomes of this research offer a new breakthrough for the design of lifting mechanism for maintaining slab track structures through the utilization of foam polyurethane slurry grouting, such as determining the optimal grouting quantity. In addition, these results are instrumental to the evaluation of lifting effects and service life, enhancing the circular economy of railway track systems.

Fatigue life assessment of a slender lightning rod due to wind excited vibrations

The wind-excited vibrations of structures induce fluctuating stresses that may result in the accumulation of fatigue damage, ultimately posing a risk of structural failure. This paper presents the findings of a research program assessing the fatigue life of a 30 m high slender and tapered lightning pole under wind induced vibrations. A three-stage study has been conducted to understand the causes of fatigue damage. In the first step, a hybrid numerical and full-scale experimental investigation was carried out to identify the natural frequencies, modal shapes and modal damping ratios. In the second step, results from the dynamic identification test were used to estimate vortex shedding induced vibrations. Critical resonant conditions on the first and second vibration modes have been investigated, adopting standards and calculation techniques from literature. Finally, in the third step, the fatigue damage induced by vortex shedding vibrations was estimated. The findings demonstrate that the fatigue issues of the lightning rod are mainly related to the wind induced stress at the base of the pole, highlighting the contribution of vortex shedding resonant with the second vibration mode. The paper also discusses the large uncertainties affecting the analysis, showing that errors in parameter estimates give rise to very large scatter in the fatigue damage assessment.

Full-scale experimental study on seismic performance of repaired precast shear walls

To improve the framework of seismic resilience assessment and design of precast concrete (PC) structures, and to contribute to the development of loss consequence functions for PC shear walls (PCSWs), a repair method for seismically damaged PCSWs using grouted sleeve connections was investigated and the seismic performance of repaired PCSWs (RPCSWs) was verified in this study. Specifically, full-scale experimental investigations were conducted involving a reinforced concrete shear wall (RCSW) as a counterpart and two RPCSWs, which were repaired based on two damaged PCSWs (one without grouting defects and the other with a 60% defect ratio) previously tested, aiming to identify the effect of grouting defects on the damage mode of PCSWs and the corresponding repair effect. Two specimens were repaired with reference to the concrete replacement method for the RCSW. The seismic performances of the RCSW, two RPCSWs, and PCSW without grouting defects were compared. Test results indicated that the damage evolution and failure modes of the RPCSWs were similar with those of the RCSW and PCSW without grouting defects. The relative differences in the loads and displacements of the critical points of the four specimens were generally less than 5.9%. Although the seismic performance of the PCSW with grouting defects was significantly different from those of the RCSW and PCSW without grouting defects, it was restored, thus verifying the reliability and versatility of the repair method. The research outcomes can provide important reference for the repair of seismically damaged PCSWs connected using grouted sleeves as well as lay a foundation for advancement of loss consequence functions for such shear walls.

Reinforced cross-laminated timber-concrete composite floor systems

This paper presents full-scale experimental investigations on cross-laminated timber concrete composite (TCC) systems. The primary objective was to determine the stiffness, ultimate load-carrying capacity, and failure modes of TCC systems using three different shear connectors: self-tapping screws, steel kerf plates, and proprietary glued-in perforated steel plates. The secondary objective was to determine the effectiveness of shear reinforcement in the CLT panels. The TCC system was comprised of 245 mm thick, 7-ply CLT panels with a 150 mm concrete topping. A total of 24 half-span (4.6 m long) and 9 full-span (9.2 m long) CLT and TCC floor segments were tested under symmetric four-point bending as well as torsional bending. For all test series, the CLT panels were either unreinforced, or reinforced using self-tapping screws. The shear reinforcement increased rolling shear capacity which helped to avoid CLT shear failure. Adding the concrete topping increased the shear capacity by up to 167%. The tests showed that the floors with steel kerf plates exhibited the highest capacity and stiffness, while also being the most easy-to-install solution. The results from this research guided project-specific design decisions for “Limberlost Place”, a mass timber building for George Brown College, in Toronto, Canada.

Full-scale experimental study on dynamic behaviors of a three-cable network with a pretensioned cross-tie

A cable network of cables interconnected with cross-ties and attached with dampers represents the generalized solution for vibration mitigation of stay cables. It is of significant interest as completely suppressing vibrations of long cables vulnerable to various excitation mechanisms is still challenging. Although many theoretical studies on cable networks exist, large-scale and full-scale experimental validations and investigations are lacking. Therefore, this study first presents a full-scale experiment setup for experimental studies on cable networks, which consists of at most three cables with adjustable length and the maximum length is 41.35 m. The experimental setup is subsequently used for studying effects of a pretensioned cross-tie on cable network dynamics, with the focus placed on the pretension, location and anchoring form of the cross-tie. The experimental results are then discussed in detail with reference to a theoretical model of a three-cable network with cable sag and cross-tie pretension accounted. It is found that the experimental results on system frequencies and mode shapes are consistent with those predicted using the analytical model. Particularly, both the pretensioned cross-tie induced increase and decrease in cable network frequencies have been validated by the experiments. Furthermore, the grounded cross-tie is found to significantly improve the system fundamental frequency, but the increase in frequencies of other local vibration modes is limited. Besides, the test results have validated that a rigid cross-tie has very limited damping effect on the cable network.

Full scale field studies for assessing the vibration isolation performance of single and dual trenches

The ground-borne vibrations induced due to construction operations transmit to the surroundings in the form of stress waves. These vibrations severely impact sensitive structures and cause human annoyance. Present solutions to vibration isolation using barriers are limited to the use of single open and infilled trenches. However, one of the significant drawbacks of using single trenches is its insignificant depth requirements. Hence, an attempt has been made to explore the possibilities of utilizing dual open and infilled trenches by conducting a full-scale experimental investigation under different frequencies of excitations. A well-accepted material, geofoam, was used as an infilling material in the two trenches of the same geometries. The influence of three different vibration locations was analyzed under five combinations of single and dual trenches. The findings from the experimental study suggest that the use of dual trenches suppresses the vibrations more effectively than single trenches. The dual open and geofoam-infilled trenches of the normalized depth of 0.3 decreased the vertical vibrations by 76% and 65%, respectively, compared to no trench conditions. Moreover, to achieve a 50% reduction in vibration, the normalized depths required for the single and dual open trenches were found to be 0.27 and 0.14, respectively.

The Effect of Microbiologically Induced Concrete Corrosion in Sewer on the Bearing Capacity of Reinforced Concrete Pipes: Full-Scale Experimental Investigation

The main part of sewer pipelines is commonly made up of precast reinforced concrete pipes (RCPs). However, they often suffer from microbiologically induced concrete corrosion (MICC), which has made them less durable than expected. In this study, three-edge bearing tests (TEBT) are performed on full-scale RCPs with preset wall losses to determine how MICC influences their bearing performance. For this purpose, several bearing indices such as D-load, peak load, ultimate load, ring deflection, ring stiffness, and failure energy are presented or specified to characterize the load-carrying capacity, stiffness, and toughness of these RCPs. It is found that crown concrete corrosion hardly changes the mechanical behavior of the first elastic zone of RCPs, so that D-load is not affected, but it shortens the crack propagation zone significantly, leading to a reduction in ultimate and peak loads. Furthermore, RCPs’ ring stiffness and toughness are negatively correlated to thickness of wall loss, while the transverse deformability of the ring cross-section is positively correlated with it. Additionally, it was found that crown corrosion affects the ultimate load of different sizes of RCP in different ways. The 2000 mm RCP is affected the most, with a 50 percent reduction in ultimate load. The 1000 mm RCP follows, with a 36 percent reduction, and the 1500 mm RCP has a reduction of less than 20 percent. This research contributes to comprehending the degradation of in-service sewage pipes, hence informing decision making on sewer maintenance and rehabilitation.

Advanced geothermal energy storage systems by repurposing existing oil and gas wells: A full-scale experimental and numerical investigation

Advanced Geothermal Energy Storage systems provides an innovative approach that can help supply energy demand at-large scales. They operate by injection of heat collected from various sources into an existing well in low temperature subsurface to create an artificial and sustainable geothermal reservoir to enable electricity generation. Very few studies investigated this approach, but those relied on hypothetical scenarios. Therefore, this study focuses on the field-scale investigation of an Advanced Geothermal Energy Storage in the low-temperature Illinois basin. A systematic preliminary data analysis was conducted to probe thermal energy storage properties of the subsurface. A full-scale field test was performed to delineate the subsurface thermal processes. Results from the field test were used to calibrate a two-dimensional axisymmetric numerical model for a single push/pull well. Various operational schemes were simulated for using the validated numerical model. The results indicated that the energy storage efficiency might reach up to 82% and the extracted fluids could generate an electrical power of 5.74 MW in five years for a simultaneous monthly injection and production scheme with an initial 90 days charging period. The proposed system which benefits from existing infrastructure, offers an economical and environmental approach for thermal storage with high storage efficiency.

Full-scale experimental investigation on the seismic performance of PC columns before and after repair of grouting defects

This research focused on investigating the influence of insufficient grouting on the seismic performance of precast concrete (PC) columns, connected using grouted sleeves, and validating the feasibility and reliability of the repair method for insufficient grouting. To realize these, five full-scale PC columns were tested under cyclic loads, including one specimen without grouting defects, two specimens with defect ratios of 45% and 60%, respectively, which were determined by previous cyclic test results of grouted sleeve connections (GSCs), and two repaired specimens which had initial defect ratios of 45% and 60%, respectively. The effects of defect ratios and repair actions were analyzed, and the test results indicated the following: 1) The bar slip dominated the failure of two specimens with defect ratios as expected, rather than the flexural failure mode for the specimen without defects. A rocking phenomenon was observed since the occurrence of bar slip, and the pinching phenomenon appeared for the corresponding hysteretic curves. The load-bearing, deformation and energy dissipation capacities were significantly lower than those of the specimens without defects. The increase in the defect ratio decreased the drift ratio associated with the bar-slip phenomenon, but the influence of the defect ratio on the seismic performance after the bar slip was negligible. 2) The bar-slip behavior was effectively prevented after the repair of insufficient grouting. Hence, the repaired specimens exhibited the expected flexural failure mode, and the load-bearing, deformation, and energy dissipation capacities were generally comparable with those of the specimen without defects. Rocking behavior and pinching phenomenon were not observed after repair. The negative influences of insufficient grouting were almost eliminated, thus validating the reliability of the repair method. The research outcome can serve as a reference for quality control of PC structures using GSCs.

A dry-connected rotational friction dissipative beam-to-column joint for precast concrete frame: full-scale experimental and numerical investigations

Simplifying the configuration, enhancing the energy dissipation capacity and achieving the adjustable performance are critical challenges in development of dry-connected beam-to-column joint. To address these, a dry-connected rotational friction dissipative beam-to-column joint (DRFDBJ) for precast concrete (PC) frame structures is developed with simple detail and adjustable performance, as well as desirable deformation capacity and energy dissipation capacity. Three solutions concerning the details and assembly sequences are recommended to ensure the expected performance. To validate the performance of the DRFDBJ and the effectiveness of the three solutions, full-scale experimental and numerical investigations were conducted. The results indicated that the desirable seismic performance of the DRFDBJ, including the damage mechanism, load-bearing capability, deformation capacity and energy dissipation capacity, were validated. The adjustable performance of the DRFDBJ was successfully achieved through accurate control of the corresponding yield load. The proposed three solutions were verified to be critical for achieving the target performance of the DRFDBJ. The research outcome can provide a valuable reference for the development of dry-connected beam-to-column joints for PC frame structures.