The technical solutions for deconstruction are reviewed and investigated in the building sector as this is an expected trend under the sustainability requirements set in the EU Commission´s “Green Deal” towards net zero greenhouse gas emissions by 2050. Two of the main research areas for efficient deconstruction strategies are; i) the behavior of multi-material structural components (hybrid structures) that combine the advantages of mechanical properties and architectural appearance of different construction materials, and ii) the techniques and mechanical properties of connections between structural components which allow deconstruction and reuse. However, there is a very limited number of studies and methods into specific demountable and hybrid structural systems, and even fewer focus on their practicability and feasibility. Since these systems have the potential to reduce construction waste, encourage resource efficiency and reduce embodied carbon impacts, it is expected that they will contribute immensely to a sustainable built environment. This paper focuses on technical solutions of the design strategies that currently have been developed for hybrid and steel reusable structural systems, and proposes an approach on implementing structural floor systems designed with the linear approach to a circular building environment.@en

To investigate the fatigue performance and fatigue damage process of the Orthotropic Steel Deck (OSD) - Ultra-High Performance Concrete (UHPC) composite bridge deck, a two-span continuous full-scale specimen was designed and tested under cyclic loading. Test results showed that the fatigue cracks firstly initiated near the lower part of the weld toe of the rib-to-cross beam welded joint, and then cracks along the weld length of the U-rib butt-welded joint developed. These observations followed by the OSD-UHPC interface debonding. The U-rib bolted joint exhibited better fatigue resistance than the U-rib butt-welded joint. The S-N curves of the rib-to-cross beam welded joint, the U-rib butt-welded joint and the U-rib bolted joint were established based on existing fatigue test data, and were compared with provisions in design codes. The S-N curves from the beam test for the short-headed stud connectors were compared with that from the push-out test. And the established S-N curves with 95% survival probability from the push-out test could be used to assess the global fatigue performance of the composite deck. Considering the durability-based critical crack width of UHPC, the established tensile S-N curve regarding critical UHPC crack width of 0.05 mm could be used to evaluate the anti-fatigue cracking ability of the UHPC layer in the composite deck system.@en

To establish the tensile constitutive model of ultra-high performance concrete containing coarse aggregate (CA-UHPC), monotonic and cyclic uniaxial tensile tests for CA-UHPC with fiber volume fractions of 2.5% and 2.0% were conducted. Test results showed that CA-UHPC exhibits approximately linear stress-strain relation up to the tensile strength, and tensile softening response composed of the smeared- and localized-cracking stages, regardless of the tested fiber contents. Based on the monotonic test data, the tensile stress-crack opening model of CA-UHPC was established, and the model was further simplified into tri-linear relation. Based on the cyclic test results, tensile damage evolution laws according to the strain equivalence principle and the energy equivalence principle were developed, respectively. Finally, the proposed tensile constitutive model and the calibrated tensile damage evolution laws were demonstrated to effectively predict the mechanical response of CA-UHPC members under both monotonic tension and cyclic tension through numerical simulations.@en

The building sector is actively researching and reviewing technical solutions for de-construction, driven by the increasing importance of sustainability requirements, as outlined in the EU Commission's ‘Green Deal,‘ which aims to achieve net-zero greenhouse gas emissions by 2050. Two key research areas in efficient structural design strategies are the performance of hybrid structures, which combine mechanical properties and architectural appearance of different materials, and the techniques and mechanical properties of connections between structural components that enable deconstruction and reuse. However, there is a scarcity of studies and methods focused on demountable and hybrid structural systems, limiting the understanding of their overall structural performance at a real-structure floor level. In this paper, a finite element model is presented to conduct a comparative study between the traditional floor system with welded stud connections and the demountable floor system with coupler-embedded bolted connectors. The numerical results showed that the serviceability loading capacity of the demountable floor system was 8% lower, and the difference in ultimate resistance was further enlarged. Reusing a demountable floor system, analysed in the case study, had little effect on the ultimate resistance, but it is difficult to exclude local plastic deformation after the first life cycles.@en

The technical solutions and design strategies for deconstruction are reviewed and investigated in the building sector in order to achieve the sustainability goals set in the EU Commission´s “Green Deal” towards net zero greenhouse gas emissions by 2050. The demountable and reusable steel–concrete composite structures could contribute immensely to the achievement of these sustainability goals. The main technical practice which allows for demountability and reusability is the use of bolted connections on the skeleton of the steel structure with the parallel use of demountable shear connectors in their floor systems with the steel load-bearing beams. However, there is a very limited number of studies and methods into specific demountable and steel–concrete composite structural systems, and even fewer focus on their practicability and feasibility. Since these systems have the potential to reduce embodied carbon impacts, encourage resource efficiency and, reduce construction waste, their feasibility and technical practices should be investigated. This paper focuses on technical solutions and design strategies that currently have been developed for steel and steel–concrete composite reusable structural systems.

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In response to the sustainability requirements set in the EU Commission´s “Green Deal” towards reduction of the greenhouse gas emissions, it is estimated that the structural design for deconstruction is going to contribute considerably to the sustainable development of the built environment. The demountability of multi-material structural systems basically depends on the shear connectors used in the structural system. This paper focuses on a type of demountable injected shear connector with an injected steel-reinforced resin (iSRR) which consists of spherical steel particles embedded in a resin. Its application to steel-to-concrete and steel-to-Fiber Reinforced Polymer (FRP) decks is presented along with its benefits. In parallel, an overview of the experimental and numerical research on the evaluation of the mechanical properties of the demountable bolted connectors with iSRR is discussed. Last, detailed finite element (FE) models and a parametric study are performed to quantify the confinement level of the SRR material influenced by the oversized hole diameter.

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Seismicity in the Delaware basin is suggested to be associated with oilfield operations. To better characterize the seismogenic structures revealed by the induced seismicity, in this study we determined source mechanisms for the Delaware basin of Texas and leveraged the obtained source mechanisms to perform stress inversion for evaluating the region’s stress state. Based on the seismogenic patterns and seismicity distribution, we identified seven distinctive seismogenic zones. Within each zone, earthquakes form several parallel-trending linear clusters. Most notably, there is an observable change in the seismicity trend on either side of the basin-bisecting Grisham fault zone. In addition, the extent of hypocentral depths vary drastically across the fault zone, with events located below the basin–basement interface north of the fault zone and more shallowly to the south. We also see spatial variations of source mechanism patterns and the direction of the maximum horizontal stress across the Delaware basin. A vast majority of seismic moment release can be attributed to the basement-rooted tectonic faults in the Culberson–Mentone seismogenic zone. A statistic deficit present in the magnitude–frequency distribution suggests that earthquakes with M_w 3.8–4.7 are needed to fulfill this scaling law. It indicates a strong possibility for future occurrence of earthquakes within this magnitude range.

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The short-headed stud connectors play a critical role on the interaction of the orthotropic steel deck (OSD) and the ultra-high performance concrete (UHPC) layer in orthotropic steel-UHPC composite bridge deck. In this paper, the fatigue behavior of these short-headed stud connectors was experimentally investigated in a beam test. The failure modes of the short-headed stud connectors were identified and classified into 5 types. The fatigue test results were analyzed by linear regression analysis neglecting run-outs and treating run-outs as failure respectively. On the other hand, the maximum likelihood estimation (MLE) approach was used to shape the S-N curve by considering the influence of run-outs. Additionally, the push-out and beam fatigue test data were compared, and the push-out test presented a relatively conservative result. Last, the applicability of existing specifications on design guidelines regarding the short-headed stud connectors design in orthotropic steel–UHPC composite bridge deck is discussed, and a design S-N curve with 95% survival probability is proposed.

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The demountable and reusable steel-concrete composite structures contribute immensely at the sustainable development in construction. The main technical practice which allows for demountability and reusability is the use of demountable shear connectors in their floor systems. These demountable shear connectors can satisfy the need for composite interaction of the steel-concrete composite floor system during its service life and in parallel the need for large nominal hole clearances during execution through oversized holes in the beam flange. These oversized holes facilitate the (dis)assembly process of the floor system. The developed demountable shear connector consists of (i) a bolt and coupler embedded in the floor, (ii) an external injection bolt through the beam flange and (iii) an injection material in the bolt-hole clearance. This injection material is a two-component epoxy resin and its benefits are focused on the increase of the stiffness and strength of the connection and the decrease of its creep deformation when compared to injected connections with conventional epoxy resin. This paper is focused on experimental of the most recent technical innovations for demountable shear connectors studied at the Delft University of Technology along with their benefits on material, connection and structural application levels.@en

Analysis of earthquake locations and centroid moment tensors (CMTs) is critical in assessing seismogenic structures and connecting earthquakes to anthropogenic activities. The objective of this study was to gain insights into the seismotectonics of the Eagle Ford Shale play (EF), southern Texas, through relative relocation of earthquakes, assessment of CMT solutions, and investigation of the background stress field. Using Texas Seismological Network (TexNet) data from 2017 through 2019, we were able to relocate 326 earthquakes and obtain CMT solutions for 37 ML ≥2:0 earthquakes. These earthquakes are located in the sedimentary basin and uppermost crust, with depths ranging from 2 to 10 km. The earthquake groups in the northeastern EF are linearly distributed along the Karnes fault zone, whereas the southern and western groups are spatially scattered around mapped or unmapped faults. CMTsolutions identified 32 normal fault earthquakes and five strike-slip earthquakes. The orientation of the fault plane of most normal fault earthquakes is southwest-northeast, whereas the possible fault plane of the strike-slip fault is from north-northwest to south-southeast, which is roughly perpendicular to the normal faults. Normal and strike-slip faults in the EF are of high dip angles, with the dip angles of the most faults ranging from 60° to 80°. Stress inversion results show that the major orientation of maximum horizontal stress (SHmax) is southwest-northeast, with minor local stress-field rotations. We further estimated earthquake energy release in the EF region using moment magnitude from the CMT solutions, and the cumulative earthquake energy release curve reveals three notable increases in cumulative seismic moment, which occurred in January-July 2018 and January-March 2019, and May-August 2019. Whether these energy releases were caused by anthropogenic activities is a matter for further investigation.@en

In this study, we present a local magnitude (M _L) relation for the earthquakes recorded from the Texas Seismological Network (TexNet) between the dates of 1 January 2017 and 31 July 2019. Using a comprehensive seismic dataset from earthquakes in Texas, we propose a distance correction term − log A ₀, which is consistent with the original definition of the Richter magnitude. The proposed distance correction calculation for the TexNet events accounts for the attenuation characteristics of the direct and refracted waves over different distance ranges. Regression analysis of Wood-Anderson amplitudes results in the following trilinear function, which represents the attenuation attributes of the events under investigation: (equcation prensent) in which R _hyp is the hypocentral distance (km). The derived distance correction relationship results in an accurate M _L relationship for Texas that is unbiased over a 200 km distance range. Compared with other M _L relations, the proposed relation in this study gives lower M _L values over all distances than those calculated by Richter (1958), Hutton and Boore (1987), Babaie Mahani and Kao (2019), and Quinones et al. (2019) by an average of 0.01, 0.12, 0.16, and 0.15 units, respectively; this study's proposed relation gives higher M _L values over all distances than those calculated by Scales et al. (2017), Yenier (2017), and Greig et al. (2018) by an average of 0.28, 0.01, and 0.08 units, respectively.

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Low-rise metal buildings are used in all geographic locations, including high seismicity regions. In the design of low-rise metal building systems, column base connections are commonly modeled as pinned supports with no rotational stiffness or moment capacity. However, past studies have indicated that base connections, which are designed as pinned supports, exhibit a non-negligible level of rotational stiffness and strength. Neglecting the rotational stiffness of the base connection may result in a significant overestimation of the lateral displacement of the frames. This additional displacement is addressed by increasing the flexural stiffness of the frame members thereby increasing the cost of low-rise metal buildings. The moment capacity may similarly be exploited for strength design. However, there is a lack of design guidelines to support the use of rotational stiffness or moment capacity at the pinned column bases. This study evaluates the applicability of existing code-formulations to pinned colum base-plate connections. Both the rotational stiffness and the moment capacity from past experiments are compared with those calculated based on the provisions of the European and American design codes. It was found that the Eurocodes do not accurately estimate the rotational stiffness of the connections. A modification to the Eurocodes is recommended to capture the characteristics of pinned connections. It was also observed that the moment capacity of the connections was conservatively estimated by the existing codes.@en

Low-rise metal buildings constitute a large portion of the nonresidential construction in the United States. These buildings are, in most cases, characterized by a pinned column-to-foundation connection. Although previous research has been conducted on other components of metal buildings (e.g., knee joints, tapered rafters), there is a lack of available data on the performance, particularly in terms of elastic stiffness, deformation capacity and energy absorption characteristics, of the pinned base-plate connections. The objective of this research is to evaluate the performance of the commonly used column base-plate pin connections in low-rise metal building systems. An experimental program is presented in which 11 column stubs were tested on concrete foundations and a systematic investigation was performed to study the influence of various parameters, including base-plate dimensions, number of anchor rods, anchor rod diameter and gage distance, on the connection behavior. The tests were performed on full-scale specimens subjected to horizontal cyclic displacements with an increasing amplitude and a constant axial load. All of the tested specimens showed high deformation capacity, and moderate strength and energy absorption. This paper presents the observed hysteretic behavior, elastic stiffness, moment and deformation capacity, and damage patterns of the tested specimens.@en