Fundamental properties associated with fluid-structure interactions are explored through precisely controlled laboratory experiments. Here, we focus on the free oscillatory response of a complex body that represents a model of bridge superstructure under a variety of water submergence levels. Under some circumstances, the resonant interaction induced by the water-wave sloshing substantially affects the oscillatory motion. The response of the structure is analyzed based on the single-degree-of-freedom system. The dynamic properties such as viscous, Coulomb and quadratic damping mechanisms, as well as the added mass are evaluated quantitatively. The data show that the added mass effect is the largest when it is fully submerged and decreases with the reduction of submergence. The added-mass coefficient is independent of the motion aligning with potential flow theory despite the presence of air-water interface. Owing to the complex configuration of the superstructure, the measured added mass coefficient is substantially greater than the theoretical value, however.

Titanium alloy bars (TiABs) have recently been accepted as a strucforced concrete structural elements. This paper shows that TiABs in NSMR applications can be used simultaneously as anodes in impressed current cathodic protection (ICCP) to prevent corrosion of the existing reinforcement. Following a successful proofof-concept study performed for small-scale prisms, dual-purpose TiABs were used as longitudinal and shear reinforcements to retrofit large-size structural beams. Prior to structural tests, the specimens were investigated to characterize the TiAB functionality within the ICCP system. During ICCP, cathodic potentials were in the expected linear region of the cathodic polarization curve of the steel reinforcing bars, and the 100 mV potential shift (decay) criterion following shutoff was satisfied upon the interruption of the protection current. The applied current and potential to achieve the required cathodic potentials were stable and were satisfactorily maintained while achieving the structural retrofit requirements.

While the use of cross-laminated timber (CLT) panels for building construction has increased over the last several decades, current standards and existing literature provide limited information regarding the design of CLT diaphragms or the prediction of their deflections when subjected to wind and strong earthquake motions. This paper presents the design and assessment of a CLT diaphragm that was part of a full-scale two-story structure subjected to shake-table testing. An analytical model is proposed for diaphragm deflection accounting for in-plane shear and bending stiffness, as well as the stiffness of various connections. Moreover, a refined numerical modeling strategy is proposed in order to consider phenomena such as panel-to-panel gap closure. Results indicate that the analytical model yields conservative results both in terms of deflections and forces when compared to the numerical model that simulates similar sources of strength and stiffness. The analytical model is suitable for the design of symmetric diaphragms with regular shapes, whereas the numerical model can also be used to model asymmetric diaphragms with irregular shapes.

Mass timber construction has seen a growing interest in North America and worldwide. In the US, code provisions allow mass timber buildings to be up to 82 m tall, but with floor slabs requiring a noncombustible, usually cementitious, topping over mass timber panels (MTPs). Designing the MTP and concrete topping to act compositely can increase the strength and stiffness compared to noncomposite MTP floors. Several connections are available to create composite action between an MTP and a concrete topping, with self-tapping screws being the most widely considered practice. A new test fixture and testing method were developed to characterize connection properties and facilitate the selection of fasteners most suitable for developing composite action. Three conventional self-tapping screws were experimentally investigated at the single-fastener scale. The screws were subjected to withdrawal at 90 degrees and 45 degrees orientations to the interface plane between the MTP and concrete. Withdrawal from both the MTP substrate and concrete topping was investigated. Three MTP materials were tested: cross-laminated timber (CLT) consisting of two different wood species and a mass ply panel (MPP). Results demonstrated that the pullout failure of the screwhead from the concrete was the limiting failure mode. Comparisons were made between the experimental results and analytical models for screw withdrawal to assess the applicability of available models to the different MTPs. These models underestimated the capacity of the tested fasteners for all samples except for the fully threaded screws.

Experimental tests of cross-laminated timber (CLT)-concrete composite floor panels were conducted. The tests consisted of linear-elastic tests of square CLT-concrete composite panels with a novel shear connector to determine elastic orthotropic plate properties. After the linear-elastic tests, the panels were subjected to a patch load at the center of the panel and tested to failure. To investigate load transfer across longitudinal joints between adjacent panels, nonuniform bending tests were conducted. Results from the experimentally measured orthotropic plate properties showed that the shear connector increased the bending stiffness in the weak direction of the panel compared to prior test results using conventional shear connectors. The tests to failure exhibited larger differences in behavior between the strong and weak orientations of the specimens, with both showing substantial inelastic behavior prior to failure. Numerical finite element models of the patch-load test showed good agreement with experimental results. Analytical formulas using the obtained orthotropic plate properties did not agree with experimental results for the patch-load at linear scales, suggesting the simplified method is currently not suited for CLT-concrete two-way bending. Load-transfer tests found that the reinforced concrete topping is capable of transferring load across the longitudinal joint of two parallel panels to enable two-way bending of composite timber-concrete floors and that the addition of a plywood spline with closely spaced screws enables a higher degree of force transfer.

The length of mass timber wall panels is a limiting factor in designing taller buildings. Splice designs are needed to maintain panel transportability while transferring shear , moment forces from higher floors to the foun-dation under lateral loading. One such splice design utilizes structural adhesive to glue threaded steel rods into the ends of wall panels being connected. This paper reports tests of the tension capacity of glued-in rods embedded in Mass Ply Panels (MPP). Twenty glued-in rods were tested under monotonic and cyclic protocols. Embedment depths ranged between 304.8 mm (12 in.) and 812.8 mm (32 in.). Load and displacement were measured during tests to report values per ISO 6891 and an international code council acceptance criteria document. Elastic stiffness, peak capacity, design capacity , a predictive capacity equation were determined. Results showed a similar stiffness for all embedment depths and a negligible difference between peak capacities from monotonic and cyclic testing. While the data reported is only directly applicable for analysis of the specific MPP and epoxy combination used in the test program, the methodology herein can be utilized for future testing of timber-adhesive glued-in rods.

The structural performance of four reinforced concrete pile cap specimens anchored by widely used proprietary high-strength threaded bars (HSTBs) and subjected to column uplift loads is investigated. The specimens were full-scale replicas of in-service foundations in terms of geometry, material properties, reinforcement details, and loading conditions. The study also included isolated pullout tests of HSTB anchorages. Two of the specimens were modified by increasing the embedment depth of the column anchor plate to assess effectiveness as a possible retrofit approach. Failure of all specimens was brittle without yielding of embedded reinforcing steel. Moreover, the ultimate pullout capacity of the anchors was not achieved in any of the specimens. ACI 318-19 provisions underestimated the concrete breakout capacity of all specimens and were unable to incorporate the beneficial effects of the column anchor plate modification as it only considered the anchor embedment length and edge distance as critical parameters for calculating strength.

The cyclic performance of substandard reinforced concrete (RC) bridge substructures seismically retrofitted using titanium alloy bars (TiABs) is assessed using full-scale experiments and nonlinear numerical models. The retrofit technique uses TiAB ligaments to simply and effectively strengthen columns with inadequate flexural lap splices and provides confinement through hoop action when combined with continuous TiAB spirals. The failure characteristics, flexural ductility, and hysteretic behavior of unretrofitted substandard (i.e., vintage) and TiAB retrofitted columns were evaluated using quasi-static, reversed cyclic tests of full-scale bridge column-footing specimens modeled after the characteristics of highway bridges in Oregon constructed prior to the introduction of seismic design provisions. Foundation rocking was examined and quantified through implementation of a soil subgrade simulant. Experimental results demonstrate improved flexural response and ductility with reduced concrete damage and residual drifts of RC columns when retrofitted with TiAB. The measured responses of the test specimens were used to calibrate three-dimensional (3D), nonlinear, finite-difference models used to investigate the effect of soil-structure interaction (SSI) on the rocking moment capacity for as-built and retrofitted column-footing specimens. The model was then used to perform a parametric study to evaluate retrofit details (flexural strength and stiffness) and soil characteristics (strength and stiffness) and their relationships to engineering demand parameters such as displacement and strength, which indicated that incorporation of SSI will permit the design of more efficient and economical seismic retrofits.

New building code changes enable mass timber panels (MTP), including cross-laminated timber (CLT), to be used in moderate and tall buildings as a floor system, usually with a concrete topping. A floor system of CLT composite with a reinforced concrete topping slab can provide increased stiffness and strength, making the system more advantageous. Present connection methods used to produce composite action within timber-concrete composites (TCC) have limitations when considering constructability or performance. This study presents experimental results from four (4) shear connectors for CLT-concrete composite floor systems, including three developed for this study. The connectors included self-tapping screws (STS) at 45-degrees, a modified lag screw with an integral plate washer that bears on the CLT surface at installation, a steel angle anchored only at the end of the span, and an inverted-T steel section with stem perforations. Different tests were performed on the different connectors including individual fastener tests, push-off group tests, and full-scale one-way bending tests. The push-off group tests showed that the proposed washer-screw exhibited higher stiffness and strength than a conventional STS. The full-scale one-way bending testing showed that the STS specimen exhibited the lowest strength of the alternatives. The inverted-T section exhibited the highest stiffness, while the other three connections had similar stiffness to the STS.

An experimental program consisting of four full-scale specimens was conducted to assess the structural behavior of very large rein-forced concrete (RC) pile caps supported on steel pipe piles. The tested specimens replicated the geometry, reinforcement details and placement, material properties, as well as support and loading conditions typical of in-service 1980s vintage pile caps. Prior to testing, three-dimensional (3-D) strut-and-tie models were devel-oped to predict the strength of the specimens and expected failure modes. During tests, widespread reinforcement yielding was observed in all specimens. One specimen failed in one-way shear, two specimens failed in two-way shear, and one specimen did not reach failure before reaching the load capacity of the test setup. Based on the experimental results, the strut-and-tie capacity predic-tions were highly conservative for all specimens and would have required retrofit of the pile caps to carry the expected column axial loads associated with a potential vertical expansion of the building. The high degree of conservatism is attributed to neglecting the beneficial effects of active confinement in the 3-D structure, espe-cially at the pile locations, that underestimates the available bond strength, thereby minimizing the available tension ties.

This paper presents the behavior of floor diaphragms of a shake-table experiment of a full-scale 2-story mass-timber building structure. The structure consists of glued-laminated timber beams and columns, and floors and walls were designed and built making use of cross-laminated timber panels. Two different floor systems were designed, where the roof consists of a topped cross-laminated timber (CLT)-concrete composite system, and the floor level consists of untopped CLT panels connected with plywood single-surface splines. The CLT floor systems were designed to remain essentially elastic over the whole series of shake-table tests, which included testing of three lateral force-resisting systems tested at three different seismic intensity levels (service level, design basis, and maximum considered earthquake) for a total of 34 shake-table earthquake tests. Results from the testing indicate that CLT diaphragms designed to remain essentially elastic based on basic principles of structural mechanics and existing test data can achieve desired seismic performance objectives. In addition, sources of overstrength in certain elements of the diaphragm need to be explicitly considered for a holistic diaphragm design. (C) 2021 American Society of Civil Engineers.

The ability of shallow bridge foundations to dissipate earthquake energy via rocking has gained significant attention by bridge engineers owing to recent efforts to quantify the performance of rocking footings. This paper presents a new formulation for estimating the moment capacity of rocking bridge foundations resting on all types of soils under varying saturation and surface flux boundary conditions. The proposed formulation uses the moment capacity equation originally employed for saturated soils, classical effective shear strength parameters, and a representation of the soil-water retention curve (SWRC) to accommodate partially saturated conditions that may commonly exist below the shallow foundations of bridge substructures. A closed-form equation is incorporated in this formulation for the matric suction and effective saturation profiles to directly implement surface flux boundary conditions when analyzing the moment capacity of rocking foundations supported on partially saturated soils. The formulation implements a new method to predict the air entry suction for partially saturated soils, representing a key step towards improving the accuracy of moment capacity. A parametric study is performed to investigate the sensitivity of the moment capacity to primary design variables and various surface flux boundary conditions. The analyses demonstrate that flow conditions have a negligible and strong influence on the moment capacity of coarse- and fine-grained soils, respectively. Predictions from the proposed formulation were compared against two sets of experimental data obtained from large-scale shaking table (on sand) and snap-back (on plastic silt) tests and indicated good agreement with experiments. (C) 2021 American Society of Civil Engineers.

A full-scale 2-story mass timber building was tested on the University of California San Diego Natural Hazards Engineering Research Infrastructure (UCSD-NHERI) uniaxial shake table during the period from June 2017 to September 2017. The main objective of the experimental program was to test the performance of mass timber building designs with different seismic lateral force-resisting systems. The focus of this study is on a building configuration designed using self-centering post-tensioned cross-laminated timber (CLT) rocking walls with U-shaped steel flexural plate energy dissipators. The shake-table tests were designed to subject the building to a series of earthquake ground motions of increasing intensity, ranging from a service-level earthquake to 1.20 times the maximum considered earthquake intensity. Between each ground motion, low-amplitude white-noise excitations were applied to the building, which responded as a quasilinear system. In this paper, two output-only operational modal analysis methods are used to estimate the modal parameters (frequency, damping, and mode shapes) based on acceleration data collected during the white-noise shake-table tests. The correlations of observed damage and repairs performed during the experimental program with changes in estimated modal features are reported. The modal parameters estimated from the testing program are also compared with a linear finite-element model that is used to validate the modal identification results and study the performance of the two system identification methods for CLT rocking structures. (C) 2021 American Society of Civil Engineers.

To accurately predict the dynamic response of a structure subjected to fluid induced loading, a thorough understanding of the dynamic properties (mass, stiffness, and damping) and associated interactions is required. Limited data are available to characterize dynamic fluid–structure interactions. Data are particularly limited for large-scale and flexible structural models. This article reports the results of the first free vibration tests of a dynamic large-scale laboratory highway bridge superstructure model. The dynamic response characteristics of the model were extracted and analyzed from free vibration tests under varying levels of water submersion and for different horizontal substructure flexibilities. The nature of the damping response was identified based on the empirically measured logarithmic decrements of the model’s free vibration displacement amplitudes, and a suitable equation of motion (EOM) was subsequently developed. Using the classical fourth-order Runge–Kutta method, the EOM was solved for the different test trials and the dynamic properties of the model were obtained through an optimization approach. The concept of added mass was introduced to explain the observed decrease in natural frequency with increasing levels of water submersion. Finally, added mass factor was computed for the case where the water level was even with the top of the bridge superstructure model. This study provides a suitable EOM needed for numerical simulations of this and similar models that study fluid–structure interaction and also provides a methodology for establishing the structural dynamic properties of generalized hydrodynamic analytical models.

Through the Natural Hazards Engineering Research Infrastructure program (NHERI) established by the National Science Foundation in the United States, a suite of experimental facilities has been made available to the research community to advance the resilience of civil infrastructure and communities to coastal storm and earthquake hazards. A NHERI Experimental Facility, hosted at the O.H. Hinsdale Wave Research Laboratory at Oregon State University (HWRL EF), was created through this program that serves as a state-of-the-art engineering research, education, and outreach center related to tsunamis caused by earthquakes and coastal waves and surge caused by windstorms. HWRL EF includes two specialized large-scale resources for physical model testing of coastal systems: a large wave flume (LWF) and a directional wave basin (DWB). These facilities are available to the research community to address grand challenges relating to tsunami and coastal windstorm surge and wave hazards impacting the built and natural environments. This paper describes the capabilities of the HWRL EF and presents 10 example projects conducted under NHERI since 2016. The research projects highlight the broad scientific interest and potential application of physical model testing in multi-hazard mitigation and resilience in coastal communities.

Designing structures resistant to tsunami-like flood flow impacts is contingent on the ability to accurately predict dynamic loading effects on building components. To characterize these effects, two metal building cladding subassembly test specimens, designed for Risk Category II and Category IV wind loading, were experimentally subjected to surges and bores with various wave height and initial water levels. The results reveal that maximum structural responses, quantified by curvatures and displacements, occur after initial wave impact, as splash up on the structure subsides. Furthermore, consistent pressure-time histories between specimens in equivalent flow conditions, despite significantly different strains and displacements, suggest structural flexibility does not influence which wave forcing produces the maximum structural response. Lastly, structural analysis of the specimens, based on measured pressures at maximum strain conditions, reveals that loading conditions ranged between hydrostatic and hydrodynamic depending on the initial flooding conditions. With these findings, a method to predict pressure magnitude and distribution on the cladding at the time of maximum structural response for tsunami-like flood flow impacts is proposed. (c) 2020 American Society of Civil Engineers.

Background: Mobile health applications (mHealth apps) targeting physical inactivity have increased in popularity yet are usually limited by low engagement. This study examined the impact of adding team-based incentives (Step Together Challenges, STCs) to an existing mHealth app (Carrot Rewards) that rewarded individual physical activity achievements. Methods: A 24-week quasi-experimental study (retrospective matched pairs design) was conducted in three Canadian provinces (pre-intervention: weeks 1-12; intervention: weeks 13-24). Participants who used Carrot Rewards and STCs (experimental group) were matched with those who used Carrot Rewards only (controls) on age, gender, province and baseline mean daily step count (±500 steps/d). Carrot Rewards users earned individual-level incentives (worth $0.04 CAD) each day they reached a personalized daily step goal. With a single partner, STC users could earn team incentives ($0.40 CAD) for collaboratively reaching individual daily step goals 10 times in seven days (e.g., Partner A completes four goals and Partner B completes six goals in a week). Results: The main analysis included 61,170 users (mean age=32yrs; % female=64). Controlling for pre-intervention mean daily step count, a significant difference in intervention mean daily step count favoured the experimental group ( p <0.0001; η p 2 =0.024). The estimated marginal mean group difference was 537 steps per day, or 3759 steps per week (about 40 walking min/wk). Linear regression suggested a dose-response relationship between the number of STCs completed (app engagement) and intervention mean daily step count (adjusted R 2 =0.699) with each new STC corresponding to approximately 200 more steps per day. Conclusion: Despite an explosion of physical activity app interest, low engagement leading to small or no effects remains an industry hallmark. In this paper, we found that adding modest team-based incentives to the Carrot Rewards app increased mean daily step count, and importantly, app engagement moderated this effect. Others should consider novel small-teams based approaches to boost engagement and effects.

The aim of this paper is to simply present live load factor calculation methodology formulation with the addition of a simple new future load projection procedure to previously proposed two methods. For this purpose, Oregon Weigh-in-Motion (WIM) data were used to calculate live load factors by using WIM data. These factors were calculated with two different approaches and by presenting new simple modifications in these methods. A very simple future load projection method is presented in this paper. Using four different WIM sites with different average daily truck traffic (ADTT) volume, and all year data, live load factors were obtained. The live load factors, were proposed as a function of ADTT. ADTT values of these sites correspond to three different levels which are approximately ADTT= 5,000, ADTT = 1,500 and ADTT ≤ 500 cases. WIM data for a full year were used from each site in the calibration procedure. Load effects were projected into the future for the different span lengths considering five-year evaluation period and seventy-five-years design life. The live load factor for ADTT=5,000, AASHTO HS20 loading case and five-year evaluation period was obtained as 1.8. In the second approach, the methodology established in the Manual for Bridge Evaluation (MBE) was used to calibrate the live load factors. It was obtained that the calculated live load factors were smaller than those in the MBE specifications, and smaller than those used in the initial calibration which did not convert to the gross vehicle weight (GVW) into truck type 3S2 defined by AASHTO equivalents.

1 Agustos 2007 tarihinde, Minnesota Amerika’da, Mississipi Nehri uzerinde bulunan, Eyaletlerarasi 35W (I-35W) adli kopru cokmustur. Bu trajik vaka, 13 olum, 145 de yarali ile sonuclanmistir. Bu uzucu kazaya celik guse plakasindaki tasarim kusuru nedeni ile olusan zayif birlesimin yol actigi tespit edilmistir. Bu trajik kaza, celik guse plaklarinin koprulerde tasariminin ve tatbikinin can alici oneme sahip oldugunu gostermistir.  Tasarim muhendislerinin celik guse plaklarinin dizaynina kayda deger ehemniyet vermesi gerekmektedir. Bu calismada celik guse plaklarin burkulma davranislari incelenmistir. Celik guse plaklarinin sonlu elemanlar yontemine gore basinc yuku altindaki analizinde, (Higgins et al., 2016 ; Scott et al., 2008) tarafindan hazirlanmis bir program kullanilmistir. Analizlerde tek eksenli gerilme sekil degistirme plastisite modeli goz onune alinmistir. Celik guse plaklarinin uc boyutlu gerilme sekil degistirme durumu tanimlanmis ve dogrusal olmayan statik analizler gerceklestirilmistir. Analizler esnasinda, celik guse plaklarina, farkli duzlem disi kusurlarin, farkli narinlik katsayilarinin ve farkli eleman boyutlarinin etkisi incelenmistir. Celik guse plakalarinda bulunan civatalarin plak icerisinde konumlarinin degisiminin davranisa etkisi de arastirilmistir. Bu parametrelerdeki degisimin,  maksimum gocme yukunun kritik Euler burkulma yuku oranina etkisi de incelenmistir. Analizler sonucunda duzlem disi kusurlarin celik guse plaklarinin basinc yukleri etkisi altindaki deplasmanlarina onemli derecede etki ettigi gorulmustur.