Lower Columns Research Articles

Deformation ability of modular gymnasium steel inner sleeve all-bolt cross connection joint based on 3D-DIC method

Immense roof loads present a significant hurdle for the functionality of continuously supported modular connection joints in movable modular gymnasium structures. Consequently, we introduced leveraging inner sleeves and bolts to interconnect the modular units of the upper and lower columns, aiming to bolster the strength of inter-unit connections. Despite its noteworthy benefits, the deformation behavior and force distribution characteristics of this novel design remain underexplored. Hence, our study employs three-dimensional digital image correlation (3D-DIC) measurement to precisely capture the full-field displacement and strain distributions within the core area of this joint. Four distinct joint specimens were designed, and conducted comprehensive static tests, encompassing variables such as the inclusion or exclusion of inner sleeves, reinforcing ribs, and diverse loading directions. 3D-DIC detected subtle deformations and local buckling phenomena, undetectable by the naked eye, and revealed their occurrence patterns. Furthermore, the detections underscore the critical role of weld quality between beams and columns in ensuring the overall safety of the joints. The joint exhibited earlier yielding in beam bending compared to column bending. To delve deeper into this joint, we generated moment-rotation curves leveraging DIC results, deducing that this joint exhibits rigid-joint characteristics. The specimens primarily showed damage modes such as beam-root fractures or member buckling, while the core area remained intact. This observation reinforces the classification of the joint as a full-strength entity. These insights enrich our comprehension of this novel joint and serve as invaluable references and aids for designers.

The Effects of Vertical Load and Gaps on Lateral Resistance of Fork-Column Dougong in Traditional MultiStory Wooden Structures

ABSTRACT This article investigates the mechanical performances of the Fork-Column Dougong (FCDG), also named as Cha-Zhu-Zao Dougong, which is a common type of connection between the upper and lower columns in a traditional multistory Chinese wooden building. Numerical results of a typical FCDG under different vertical loads illustrate that the vertical load can strengthen the lateral stiffness of FCDG to some extent. Because existing FCDGs have different lengths of column limbs in their construction, the effect of this variation on the lateral behavior of the FCDG is also studied with reference to the different contact states between different components of the FCDG. The FCDG without gaps between its components gives generally better lateral behavior according to the lateral force-displacement curve. Because the column is the main member of the structure to carry the structural load transferred through by contact between the column limbs and the supporting Fangs. The length of column limbs would directly affect the effective contact area at the bottom and roots of column limbs, and the variation of the contact area would change the bearing capacity and load path of the FCDG. Results from this study may serve as reference to the restoration and protection of traditional Chinese wooden structures.

Deformation ability of steel inner sleeve T-joint in modular gymnasia based on 3D-DIC method

Substantial loads the roofs bear exert stringent performance standards on connecting joints in movable modular gymnasiums. Previously, we introduced a novel joint design, utilizing internal sleeves and bolts to integrate the upper and lower columns of modular units. To explore the actual deformation behavior and force distribution of this joint, this study employed a three-dimensional digital image correlation (3D-DIC) measurement method to visualize its full-field displacement and strain distribution. The reliability of the 3D-DIC results was confirmed through comparison with traditional measurement methods. Building upon this solid foundation, this study proceeds to assess the static performance of this innovative joint in two distinct directions, successfully revealing micro-deformation and local buckling phenomena undetectable to the naked eye. Notably, the quality of the welds connecting the beams and columns plays a pivotal role in ensuring the overall structural integrity of the joint. Under lateral loading conditions, the destructive behavior of the joints is primarily governed by material strength. Moment-rotation curves were plotted to delve further into the mechanical characteristics of the joint, revealing that the inner-sleeve T-joint exhibits the attributes of a rigid joint. Moreover, the primary damage modes observed in the specimens were fractures at the beam root or buckling of the column, with the joint area remaining intact. Consequently, this joint qualifies as a full-strength connection. These findings will deepen knowledge and understanding of this novel joint for designers.

Experimental study of the static and hysteretic performance of grouted steel beam-column inter-connections for modular integrated construction

Modular Integrated Construction (MiC) has gained prominence as a construction method, and the integrity of its structural connections plays a critical role in ensuring the overall stability and safety of buildings. This paper presents an experimental investigation into the static and hysteretic performance of grouted steel beam-column inter-connections designed for MiC. The study examines eight full-scale specimens subjected to both monotonic and cyclic loading conditions, with a focus on failure characteristics, deformation behavior, loading-displacement curves, loading-strain curves, skeleton curves of hysteretic loops, stiffness degradation, and energy dissipation. Key findings of the study include the observation of weld cracking between beam flanges and columns in all specimens, highlighting the necessity of welding quality control to prevent such issues. Grouted connections exhibited superior integrity, with no gap opening or misalignment between upper and lower columns. Additionally, it was found that grouting could enhance the stiffness of certain connections. Removal of diagonal stiffeners significantly decreased peak bearing capacity, emphasizing their importance. The composite action brought about by bolts connecting ceiling and floor beams also proved influential. According to Eurocode 3, all grouted specimens fall under the classification of semi-rigid connections, with a distinction made for partial and full-strength connections. This research contributes valuable insights into the static behavior and hysteretic performance of grouted steel beam-column inter-connections for MiC, providing essential knowledge for the structural design and safety of buildings utilizing this innovative construction method.

Jet grouting to new depths in the Lambeth Group and Thanet Formation beneath London

A jet grouting trial was undertaken within the Thames Tideway Tunnel shaft at Kirtling Street in Battersea, SW London, to assess the viability of the technique within the Lambeth Group and Thanet Formation sediments up to 60 m below ground level. There was no precedent industry experience of jet grouting in the UK at this depth and in these soil types. Four, separate, upper and lower grout columns were constructed respectively within upper and lower granular zones inside the shaft footprint, and then exhumed for inspection and measurement during ensuing excavation within the diaphragm wall lining. Target diameters for the upper columns were achieved within granular channel sand and Laminated Bed material, with minimal vertical deviation. These were not so successfully achieved, however, within stiff cohesive Laminated Bed and Lower Shelly Clay materials. Formation of the lower columns was severely restricted in dense gravel belonging to the ‘Pebble Bed’ and stiff gravelly clay, at the top of the Upnor Formation, but target diameters were being achieved in the lower portion of the formation, comprising Upnor sand. At their base, the column diameters were, again, restricted in the very dense sand at the top of the Thanet Formation.

Nitrogen isotopes and geochemistry of the basal Datangpo Formation: Contrasting redox conditions in the upper and lower water columns during the Cryogenian interglaciation period

The late Neoproterozoic witnessed series of remarkable geological evolutions, including the Sturtian and Marinoan glaciation events during the Cryogenian. A stratified oceanic redox structure has been proposed for this period, and the dynamics of the deep water redox conditions have been well illustrated by trace metals and their isotopes. However, variations in the redox conditions of the upper water column have received much less attention. Sedimentary nitrogen isotopes (δ15N) are critical for reconstructing the redox conditions in the upper water columns of ancient oceans. Existing research on the N cycle during the Cryogenian period is scarce, and the majority of studied samples were collected from shallow and medium water depth facies. To address this paucity of studies, we conducted a high-resolution N isotope study in combination with Fe speciation and Mo concentration data from two deep-water sections of black shales in the basal Datangpo Formation in the Nanhua Basin, a typical organic-rich stratum deposited during the Cryogenian interglaciation period. While the trace metal proxies suggest a fluctuating euxinic–ferruginous bottom water column for the lower interval and a stable euxinic bottom water column for the upper interval, the redox conditions of the upper water column were relatively stable, as indicated by minimal changes in the recorded δ15N values. Furthermore, the δ15N values of black shales in the basal Datangpo Formation of the Nanhua Basin have a limited range (3.1‰ − 5.8‰, average of 4.3‰, standard deviation (SD) = 0.5‰, n = 104) and show no water-depth gradient, indicating the presence of a relatively large and stable nitrate reservoir and a deep redox chemocline in the Nanhua Basin. The characteristic of the nitrate reservoir reflected by these δ15N signals can be roughly analogized to the global interglacial ocean, although only the counterpart northeast Svalbard can be used for comparison. Therefore, the nitrate availability in the marine water column may have had little effect on animal radiation during the Cryogenian interglacial period. These findings help to clarify the N cycle in the Cryogenian Nanhua Basin and shed light on its significance on bioevolution.

Effect of ultra‐high performance concrete repair layer thickness on the behavior of concrete columns

AbstractThe use of ultra‐high‐performance fiber reinforced concrete (UHPFRC) to repair or rehabilitate old concrete structures has been shown to be appropriate due to its properties, such as higher compressive strength, ductility, and durability than conventional concretes. One of the studied strengthening techniques is the reinforced concrete columns jacketing by UHPFRC. Some recent research evaluated some parameters, such as the repair thickness and the volumetric ratio of stirrups. However, other important parameters, such as UHPFRC jacketing thickness in different column cross‐sections and the concrete core compressive strength, need to be addressed. In addition, the analytical models presented in the literature are restricted to only one concrete grade. The present study aims to evaluate the behavior of short reinforced concrete columns strengthened with UHPFRC subjected to centered compression. Numerical analyses of three‐dimensional models were performed using the finite element method, validated, and calibrated using experimental results. The influence of the concrete core compressive strength, the UHPFRC jacketing thickness, and the shape of the cross‐section were evaluated. Numerical simulations concluded that the lower concrete core compressive strength columns showed the best relative increase performance. Moreover, the concrete core strength was inversely proportional to the resistance capacity of the repair system. In addition, the increase in repair thickness contributes to the axial strength of the column. Furthermore, the cross‐section influences the distribution of stresses and strains, showing the best performance for circular sections. Finally, regardless of cross‐section type, the proposed equations accurately predicted the numerical results.

Mechanical performance study of a novel modular gymnasium inner sleeve all-bolt cross connection joint – part Ⅰ: Experiments and finite element modeling

The authors propose a novel movable modular gymnasium based on modular building technology to meet people's sports needs. However, the huge roof load puts higher requirements on the performance of modular units and their connecting joints. In light of this, the authors propose a novel connection joint using the inner sleeve and bolted connections, which connect the upper and lower columns of the modular unit to give it higher performance. In addition, it connects the upper and lower beams of the modular unit by bolts to improve its overall performance. The authors evaluated the mechanical properties of the connecting joints through experiments and simulations. The results indicate that the welding quality determines the beam-oriented bearing capacity of the connections while having little impact on the column-oriented bearing capacity. It is difficult for the inner sleeve to enhance the initial stiffness and beam-oriented bearing capacity of the joints due to the initial gap between the inner sleeve and the modular column. The restraint effect of the stiffening ribs induces the deformation of the inner sleeve, and its bearing capacity increases up to 91%. The inner sleeve improves the column-ward bearing capacity and deformation capacity of the joints, and its bearing capacity rises to 135%.

Experimental and numerical simulation study of mechanical properties of inner sleeve T-joint in modular gymnasia

In response to the contradiction between the insufficient number and unreasonable distribution of stadiums in cities and the increasing demand of people for fitness, the authors propose movable modular gymnasiums. This gymnasium takes advantage of the modular building, which can be quickly built, dismantled, and reassembled to fully utilize the temporary empty land in the city to meet the fitness demand of the people. However, the box modules bear a huge roof load, which puts higher demands on the performance of the modular units and their connecting joints. This study proposes a novel joint using an inner sleeve and bolted connections. The proposed connection uses an inner sleeve and bolts to connect the upper and lower columns of the modular unit to give it a higher bearing capacity. Bolts connect the lower unit's ceiling beam and the upper unit's floor beam to provide a better overall performance of the modular unit. The authors conducted experimental studies of 2 full-scale models and 24 finite-element parametric analyses. The results show that the welding quality determines the beam-ward bearing capacity of the joints, while it has little effect on the column-ward bearing capacity. In practical engineering, the authors suggest that the initial stiffness of the joints does not consider the contribution of the inner sleeve. The setting of stiffening ribs forces the inner sleeve to deform and force, improving the joints' mechanical properties, with the initial stiffness in the column direction increase of 25 %, the initial stiffness in the beam direction increase of 31 %, and a bearing capacity in the beam direction increase of 38 %. The design thickness of the inner sleeve and stiffening ribs should be close to the wall thickness of the modular beam and column. The results of this paper contribute to the development of fitness for the whole population and the expansion of the application of modular buildings.

ASSESSMENT OF TIDAL ENERGY RESOURCES IN BALI STRAIT

The ocean possesses advantages as a sustainable and predictable source of energy, with tidal energy being one such marine-derived energy source. This study examines the analysis of ocean energy potential in the study location of the Bali Strait. The analysis of tidal energy potential follows the guidelines of the European Marine Energy Center (EMEC) and employs numerical modeling to identify current velocities using Delft3D. This study investigates the influence of water depth columns to determine the optimal depth for the placement of energy conversion technologies. It is found that the highest current velocities occur in the strait's narrowed section. Furthermore, from the analysis of tidal energy potential, it is determined that upper water depth columns (9 m, 19 m, and 26 m) can generate twice as much energy as the lower water depth columns (40 m and 45 m).

Innovations for Bolted RHS Column Splices

AbstractTwo novel concepts, recently developed in North America, are presented for bolted splices between Rectangular Hollow Section (RHS) column members. Single‐sided bolting through the RHS wall is performed, but using regular high‐strength bolts rather than “blind bolts”. The first concept employs nut‐holding devices, called “Shurikens”, that are pre‐installed on four splice plates fitted to the inside of the two RHS columns. The second innovation is a custom‐designed, hollow, cast steel insert – made of nut‐quality steel – that extends into both the upper and lower columns and has threaded holes to receive the inserted bolts, in lieu of nuts. This “internal plug” is a pre‐engineered solution, tailored to a particular RHS size, and requires no connection design. For both concepts, a bolted shear connection with little protruding steelwork is the result.

Experimental research on interfacial bonding performance of high‐strength steel pipe and surrounding concrete/grout for assembled composite columns

AbstractHigh‐strength steel pipe joints are proposed for assembled composite columns. The steel pipe extends into the upper and lower prefabricated columns and is anchored by poured concrete or grout to realize the connection of the prefabricated columns. Bonding performance of high‐strength steel pipe and surrounding concrete/grout is critical to the joint reliability. Steel pipe push‐out test was carried out, considering parameters of steel pipe section specification, bonding length, bonding material, and outer wall treatment of the steel pipe. Comparative analysis of measured load–displacement/slip curves and calculated bond strength were conducted. Bonding length of 600 mm could provide sufficient bond strength. Increasing bonding length could delay the slippage, but the bond strength decreased. High‐strength grout significantly increased the peak load size. The slenderness ratio and diameter–thickness ratio of the steel pipe had no obvious influence on the bonding performance. Steel pipe with D114*25 section obtained higher bonding strength with smaller ratio of bonding area to cross‐sectional area. Spiral ribs welded to the outer wall of the steel pipe could effectively improve the bonding strength and delay the interface slip. With easy construction and reliable performance, spiral ribs were recommended to be applied in prRactical projects.

Tidal Currents in Douglas Channel, British Columbia: Evaluation and Prediction

Douglas Channel is the principal shipping route between the town of Kitimat and the Pacific Ocean. Prediction of near-surface currents is crucial for safe tanker navigation and cleaning-up oil spills. Three years of current velocity data were collected at two moorings located 30 km apart. Spectral, wavelet, and harmonic analysis of measured currents throughout the upper (40-m) and lower (50–358 m) water columns indicated the predominant influence of semidiurnal (SD) tidal currents. In the upper layer, wind and density flows resulted in considerable seasonal and interannual variability of these currents. Analysis of the SD variance reveals three major components: barotropic, coherent baroclinic, and random baroclinic. The predictability of near-surface currents depends on the relative contribution and stability of the first two components. Tidal constants estimated for one year were used to predict currents for two other years; we found that at the mooring closer to the entrance of Douglas Channel, 80 to 89% of the SD energy in the upper layer and 89–93% in the lower layer can be forecasted, while closer to the two channel head, these numbers are smaller: 55–70% and 79–89%, respectively.

Climate-driven intensification of hypolimnetic deoxygenation in Lake Fuxian, a monomictic lake in south-western China, since the 1990s

In monomictic lakes, the potential intensification of hypolimnetic deoxygenation due to human activities and climate change threatens lake ecosystems and water quality. Understanding the trends and mechanisms of hypolimnetic deoxygenation would allow for the adaptive management of monomictic lakes. This study investigated the trends and drivers of hypolimnetic deoxygenation in Lake Fuxian (a monomictic lake in south-western China) over the past 150 years using paleolimnological evidence and historical records. Analysis of enrichment factors for molybdenum (Mo), uranium (U), and vanadium (V), and ratios of U/thorium (Th), pristane (Pr)/phytane (Ph), and total organic carbon (TOC)/total phosphorus (TP) in a dated sediment core indicated that the extent of hypolimnetic deoxygenation was relatively low before 1994 and increased substantially thereafter. Nutrient monitoring records and sediment n-alkane proxies indicated notable eutrophication of the lake since 1986 and a greater degree of human disturbance in the catchment between 1951 and 1967. Due to their asynchronous occurrence, eutrophication and catchment disturbance could not be the major drivers of hypolimnetic deoxygenation. Interestingly, climate records indicated that the local ambient temperature exhibited similar trends to that of hypolimnetic deoxygenation, including markedly higher temperatures after 1994. This implies that prolonged water column stratification due to climate warming could have promoted hypolimnetic deoxygenation by limiting oxygen exchange between the upper and lower water columns. In comparing the results with those of Lake Erhai, another monomictic lake with contrasting morphology and hydrology characteristics, we found that the low surface area/depth ratio and long water residence time in Lake Fuxian enable dissolved oxygen of the lake hypolimnion vulnerable to temperature over the lake.

Stress Distribution on the Preliminary Structural Design of the CENTEC-TLP under Still Water and Wave-Induced Loads

An assessment is made of the stress distribution and the hydrodynamic response of the preliminary structural design of the tension leg platform of a 10 MW wind turbine. The platform supporting a 10 MW turbine is modelled and analysed by the finite element method. The stress distribution of the platform is determined in still water with the turbine at above-rated conditions, and the response of the tension leg platform is estimated in the time domain. The results of the time domain analysis show reasonable agreement between the present results and the available data. To check the design stiffener dimensions, span, and spacing against stress distribution, classification societies’ recommendations are used. The results of the stress distribution analysis indicate that the critical locations of the platform are the interaction of the lower columns with the upper columns and the connection of the tower of the turbine.

Experimental study on seismic behaviour of precast recycled fine aggregate concrete columns with pressed sleeve connections

In this paper, the seismic behaviour of precast recycled fine aggregate (RFA) concrete columns with pressed sleeve connections was investigated experimentally, in order to prove the potential for utilising RFA and pressed sleeves in new concrete construction. The upper and lower columns of the specimens were manufactured using recycled aggregate concrete (RAC) and the longitudinal reinforcements were connected by pressed sleeves during assembly on site. Ten columns with 400 mm × 400 mm cross-section were designed and tested under cyclic loading, considering various parameters including the axial compression ratio (from 0 to 0.55), longitudinal reinforcement ratio (1.01 %, 1.59 % and 2.45 %), replacement ratio of RFA in concrete (0, 30 % and 70 %) and manufacturing method (cast-in-situ and precast) for comparison. Their failure process, hysteretic behaviour, strength, stiffness and ductility as well as energy dissipation were studied. The specimens all experienced cracking, yield, ultimate and failure phases during the test. The ultimate drift angle ranged from 1/57 to 1/16. The lateral bearing capacity of the specimen increased with the augment of the axial compression ratio or the longitudinal reinforcement ratio within the range of experiment parameters. The experimental results demonstrated the favourable performance of longitudinal reinforcements connected by pressed sleeves, and the feasibility of using RFA concrete in this type of precast column. The theoretical calculation for the strength of the columns based on Chinese code GB 50010-2010 and American code ACI 318-19 was then performed, and the obtained results were compared with the experimental ones. It was shown that the experimental flexure-compression strengths were 0.99 ∼ 1.25 and 1.03 ∼ 1.34 times the theoretical values calculated based on GB 50010 and ACI 318, respectively, which indicated the calculation methods proposed in current concrete structures codes could be used as references for the structural design of the precast RFA concrete columns with pressed sleeve connections.

Seismic behaviour of I-beams bolted CFST column connection using extended TSOBs

In this paper, the structural response and design method of Extended T-head Square-neck One-side Bolts (Extended TSOBs) bolted I-beams to Concrete Filled Steel Tubular (CFST) column cruciform connection were investigated under cyclic load through experimental, numerical, and theoretical approaches. The study mainly reports the effects of H-steel stiffener on seismic performance indices such as failure mode, bending bearing capacity, strength and rigidity degradations, and energy dissipation of the connection. Test results show that: (1) The H-steel stiffener can prevent Extended TSOB pull-out failure, but the relative slippage between the upper and lower columns is introduced in the strengthened connection; (2) The H-steel stiffener improves the peak bending moment, ultimate rotation, and accumulated energy dissipation of the connection by 3.3 %∼8.3 %, 33.9 %∼63.1 %, and 100.3 %, respectively; (3) The test connections can be classified as semi-rigid and partial strength joints according to Eurocode 4. The Finite Element Model (FEM) parametric analysis results show that Extended TSOB can be replaced by TSOB in the connections with H-steel stiffener and increasing the concrete grade has little effect on improving the connection bending bearing capacity. Moreover, two analysis models for calculating the bending bearing capacity of Extended TSOBs bolted I-beams to CFST column cruciform connections are proposed based on theory and tests. The accuracy and reliability of the proposed models are verified by comparing the calculated and tested bearing capacities.

Effect of concrete edge distance on the hysteretic response of roof joint

SummaryRoof joint connects the upper roof structure to the lower RC columns in large‐span structures. However, during several earthquakes, concrete edge failure of roof joint observed in several previous earthquakes shows potential collapse damage of the large‐span structures. This paper presents an experimental and numerical study on the performance of roof joints under quasi‐static cyclic loading. The effects of concrete edge distance of anchor rods and using horizontally slotted holes in the base plate were investigated and discussed by means of ultimate shear resistances, failure modes, hysteretic responses, anchor strains, and stirrup strains. It was found that concrete edge failure was prone to occur if the edge distance was taken as per current design practice. However, with the use of slotted holes in the base plate, the concrete edge failure could be suppressed due to the sliding between the base plate and the mortar layer. A refined theoretical model was proposed to evaluate the ultimate shear resistance and predict the failure mode. Finite Element Models (FEMs) were also developed to verify the proposed theoretical model in terms of the ultimate shear resistance and the failure mode under both monotonic and cyclic loading.

Validation of Copernicus Sentinel-3/OLCI Level 2 Land Integrated Water Vapour product

Abstract. Validation of the Integrated Water Vapour (IWV) from Sentinel-3 Ocean and Land Colour Instrument (OLCI) was performed as a part of the “ESA/Copernicus Space Component Validation for Land Surface Temperature, Aerosol Optical Depth and Water Vapour Sentinel-3 Products” (LAW) project. High-spatial-resolution IWV observations in the near-infrared spectral region from the OLCI instruments aboard the Sentinel-3A and Sentinel-3B satellites provide continuity with observations from MERIS (Medium Resolution Imaging Spectrometer). The IWV was compared with reference observations from two networks: GNSS (Global Navigation Satellite System) precipitable water vapour from the SuomiNet network and integrated lower tropospheric columns from radio-soundings from the IGRA (Integrated Radiosonde Archive) database. Results for cloud-free matchups over land show a wet bias of 7 %–10 % for OLCI, with a high correlation against the reference observations (0.98 against SuomiNet and 0.90 against IGRA). Both OLCI-A and OLCI-B instruments show almost identical results, apart from an anomaly observed in camera 3 of the OLCI-B instrument, where observed biases are lower than in other cameras in either instrument. The wavelength drift in sensors was investigated, and biases in different cameras were found to be independent of wavelength. Effect of cloud proximity was found to have almost no effect on observed biases, indicating that cloud flagging in the OLCI IWV product is sufficiently reliable. We performed validation of random uncertainty estimates and found them to be consistent with the statistical a posteriori estimates, but somewhat higher.

Unexpected Repartitioning of Stratospheric Inorganic Chlorine After the 2020 Australian Wildfires

AbstractThe inorganic chlorine (Cly) and odd nitrogen (NOy) chemical families influence stratospheric O3. In January 2020 Australian wildfires injected record‐breaking amounts of smoke into the southern stratosphere. Within 1–2 months ground‐based and satellite observations showed Cly and NOy were repartitioned. By May, lower stratospheric HCl columns declined by ∼30% and ClONO2 columns increased by 40%–50%. The Cly perturbations began and ended near the equinoxes, increased poleward, and peaked at the winter solstice. NO2 decreased from February to April, consistent with sulfate aerosol reactions, but returned to typical values by June ‐ months before the Cly recovery. Transport tracers show that dynamics not chemistry explains most of the observed O3 decrease after April, with no significant transport earlier. Simulations assuming wildfire smoke behaves identically to sulfate aerosols couldn't reproduce observed Cly changes, suggesting they have different composition and chemistry. This undermines our ability to predict ozone in a changing climate.