Arch Action Research Articles

Experimental study on progressive collapse behavior of frame structures triggered by impact column removal

In the research field investigating the progressive collapse of building structures, event-dependent collapse processes have gained increasing attention in analytical and numerical studies. Different events could cause varying effects on progressive collapse resistance. The alternate load path could be related to events that could also lead to variations in load actions. However, experimental studies on reinforced concrete (RC) frame structures triggering structural column removal by the low-velocity impact have not been reported. Therefore, this paper performed an initial experimental study employing impact loading as the extreme event to investigate subsequent progressive collapse behavior of structures. Tests were conducted on six RC substructures consisting of a two-span beam and a structural column. Gravity loads were applied to the top of substructures, and a pendulum impact setup was utilized to remove RC columns by low-velocity impact. When the column underwent lateral failures, the downward force exerted by longitudinal steel bars of the column, before they fractured, pulled the two-span beam beyond the compressive arch action (CAA) stage, leading to a collapse process entirely different from their event-independent counterparts. The parametric study based on experimental results indicated that low-elevation impact and increase of column longitudinal bars detrimentally affected the performance of two-span beams resisting progressive collapse, while the increase in concrete strength partially improved the residual bearing capacity after impact column removal (ICR). Based on a dynamic model, a simplified calculation method is proposed for quantifying the downward force.

Simplified discontinuous field model for RC beams with a medium shear span ratio: Experimental study and shear strength formula

It is generally believed that the shear span ratio is one of critical factors governing the shear failure of reinforced concrete beams. For a certain shear span scenario, the shear transfer mechanism is often attributed to one of the two typical categories: ‘beam-action’ for slender beams with a large shear span ratio, and ‘arch-action’ in deep beams with a small shear span ratio. However, in the medium shear span ratio range, neither the beam action nor the arch action dominates. In this study, an alternative model based on the notion of discontinuous fields is established under the framework of limit analysis. A shear strength formula for medium shear spans is derived subsequently by solving a combined action of the smeared-arch subfield and the vertical stirrups linking the fan subfield. After that, the least shear strength is obtained via the kinematic analysis of these discontinuous fields. To examine the proposed model, an experimental study is conducted through two T-beam specimens with artificially preset cracks and two benchmark specimens. In comparison with existing approaches and test results collected from this study and other twenty-two specimens in the literature, the proposed discontinues field model has a fairly good agreement in the shear strength predictions. A further discussion on the advantages and limitations of the simplified discontinuous field model also demonstrates that it provides a better transition of the shear strength verifications between slender beams and deep beams.

Numerical study of cutterhead-soil interaction in dry sand

ABSTRACT This paper presents a numerical study on cutterhead-soil interaction and its influence on tunnel face stability for stationary and rotating cutterheads. A parametric study was carried out for different friction angles, cover depths, and face pressure. The results indicate that the required face pressure is influenced significantly by the cutterhead-opening-soil interaction. As face pressure is progressively reduced from a high value, stability of the soil across an opening is initially maintained by arch action. The transfer of load from the opening to the springers of the arch leads to an increase in cutterhead thrust. This reaches a peak value after which the arch collapses. A higher friction angle of the soil allows the arch to remain arched at lower face pressure. Under torque-free condition, a higher cutterhead-soil interface friction coefficient enhances stability slightly by mobilizing friction resistance on the soil at the springers of the arch.

Graphical poly-arch model for the ultimate limit state verification of RC deep beams under hanging loads

The structural behavior of RC deep beams under hanging loads differs from that of conventional top-loaded beams. The hanging loads that are applied at the bottom of beams impose a remaining arch action and an intersecting tension field below such indirect load-carrying mechanism can be recognized, which are not dealt well with existing design approaches. Correspondingly, a graphical poly-arch model is developed for the ultimate limit state verification of RC deep beams under hanging loads, in which the function of interior inclined ties linking the arch rib and the longitudinal tie is acknowledged. Based on the connection between graphic statics and strut-and-tie models, the graphical analysis of proposed poly-arch models using reciprocal diagrams is also presented. After that, the proposed graphical poly-arch model is examined by two case studies, in which the predictions have a fairly good agreement with test results with different span-length-to-depth ratios. Furthermore, the advantages and limitations of the graphical poly-arch model are discussed. As an upgrade over existing strut-and-tie models, it can be seen that the graphical poly-arch model is highly valuable for organizing the load paths within RC deep beams under hanging loads and provides a clear mechanical explanation of how the inclined ties and the longitudinal ties interact, and what failure patterns govern.

Improving shear performance of regular web openings concrete beams using steel mesh reinforced strain hardening cementitious composites: An experimental and numerical study

The majority of studies focused on shear strengthening methods for single or double transversely opened reinforced concrete (RC) beams; however, no studies examined beams with multiple openings. This study looked at the shear response of 10 RC beams with multiple openings that were strengthened with externally strain-hardening cementitious composites (SHCC) and supplied with various layers of steel mesh fabric (SMF). The square or circular shape of the openings, the use of internal stirrups, and the use of one, two, or three layers of SMFs to support the SHCC layer are investigated. Analysis was done on the beams' stiffness, ductility, ultimate load and corresponding deflection, load-displacement response and failure pattern. In the experimental program, the shear span-to-depth (a/d) ratio was 2.4 for each of the ten beams. To further examine the impact of the same key parameters on the shear response of the beams at an a/d of 1.2, a non-linear finite element model was built. The experimental results showed that dense stirrups beam, one layer SMF-beam, two layers SMF-beam, and three layers SMF-beam achieved improvements in the ultimate load of 21.3 %, 34.6 %, 38.6 %, and 47.3 %, as well as increases in the rigidity of 6.4 %, 9.4 %, 51.7 %, and 53.6 %, and gains in the ductility of 78.4 %, 28.5 %, 547 %, and 357 % when compared to comparable control beam with circular openings. The numerical results indicate that strengthening SHCC layers outperforms better for RC beams with a smaller a/d rate and that follow the arch action in the critical shear zone.

Influence of arch action on load-carrying capacity of double-sized industrial precast slabs: A combined numerical and experimental study

The precast industry offers slab panels of different geometries according to the field conditions. These slab panels are popular in temporary constructions and beneficial in sustainability but have some financial limitations and local constraints. For a long time, the construction industry has used the arch action method, which restricts the stresses to the compression zone in concrete members and develops the required load-carrying capacity. For the same motives, industrial buildings have preferred semi-circular precast roofs, but the morphology was not suitable. For the proposed slab in this research, firstly, the typical industrial precast slab panel was doubled in width to minimize the time and efforts required for its casting, curing, and placement. Secondly, that doubled-in-width slab was provided with the arch action to confine the stresses to compression and benefit from the section entirely. Lastly, the top of the slab was kept flat to take advantage of the roof space. All these changes aimed for structural stability, reduced material's weight, improved load-carrying capacity, appropriate mobilization, and financial viability. A numerical approach and practical testing were adopted using the finite element modeling software, ABAQUS, to analyze load–deflection responses of both slabs through the concrete damage plasticity model. The proposed slab exhibited better performance as its capacity enhanced by about 1.5 times that of a typical slab. Although the volume of the material in the proposed slab increased slightly from 0.040 m3 to 0.045 m3, the reductions in joint filler materials, reinforcements, and efforts required for mixing and lifting machinery compensated for this increase significantly. Hence, the slab can be recommended for the industry to save the costs while taking heavier loads efficiently.

Progressive collapse resistance of local prestressed concrete sub-structures: Numerical analysis and theoretical verification

The local prestressed concrete (LPC) structure is a structural form that combines the prestressed concrete (PC) span with the common reinforced concrete (RC) span, with significant asymmetry. Currently, there is insufficient research on the progressive collapse resistance of LPC structures. To investigate the progressive collapse mechanism of LPC structures, a parametric analysis was conducted by using the finite element software OpenSEES. Based on the failure mode of LPC structures, the proposed method predicted the limit state by considering displacement coordination, force equilibrium, and the influence of the plastic hinge regions. The research showed that LPC structures exhibited a distinct transition action stage (TAS) between the compressive arch action stage (CAAS) and catenary action stage (CAS), which distinguished them from the symmetrical structures. Increasing the strand area could significantly improve the catenary action (CA) of the LPC structure and extend the TAS. Lengthening the PC part also improved CA and allowed the structure to progress into TAS and CAS earlier. By increasing the length of the RC part, the compressive arch action (CAA) could be strengthened, while the duration of CAAS was extended. The theoretical prediction method proposed in this study can effectively predict the ultimate displacement and ultimate resistance of LPC structures.

Effect of three-dimensional space on progressive collapse resistance of reinforced concrete frames under various column removal scenarios

In this study, high fidelity finite element (FE) model was adopted to investigate the progressive collapse resistance of reinforced concrete (RC) frame structures under various column removal scenarios. The validity of the numerical model was verified by comparing with the existing experimental results. Afterwards, to facilitate the research on possible simplified boundary conditions served for further various column removal scenarios, the effect of multi-span continuous beams was firstly evaluated and the simplified methods were compared. Then, the effect of various column removal scenarios addressing the three-dimensional effect on the progressive collapse resistance of RC frame structures with and without slab was systematically evaluated. The analysis results showed that the continuous span beams increased the internal compressive force of the beam section at compressive arch action (CAA) stage, which effectively improved the CAA strength of the substructure. For simple modeling, the use of horizontal constraints at the end of the beam could replace the continuous span beams. The presence of transverse beams and slab provided additional load transfer paths for collapse resistance. The compressive membrane action (CMA) and tensile membrane action (TMA) of the slab significantly improved the progressive collapse resistance of the substructure in the small and large deformation stages, respectively. The location of the removed column significantly affected the contribution ratio of transverse beams and slab to the progressive collapse resistance of the substructure, which was quantitatively evaluated for practical design.

Experimental study on the progressive collapse resistance of emulative precast concrete beam-column subassemblies with various anchorage details

In this study, seven emulative precast concrete (PC) beam-column subassemblies with or without connecting bars and one concrete (RC) were fabricated and tested to investigate the effect of various types of anchorage detailing for reinforcing and connecting bars on the progressive collapse resistances. Two anchorage detailing formats for steel bars with bending and straight ends were used in the PC specimens for both the reinforcing and connecting bars. Test results show that, as found in the RC specimen, resisting mechanisms including pure flexure, compressive arch action (CAA) and tensile catenary action (TCA) were sequentially activated in all PC specimens. It is demonstrated that the connecting bars improved the progressive collapse resistance in both the CAA and TCA stages. The effect of the anchorage detailing was found to be negligible in CAA stage. However, in the TCA stage, the proper usage of the straight end for steel bars was helpful to improve the deformation capacity and thereafter enhanced the progressive collapse resistance. When the loading resistance, the deformation capacity as well as the construction flexibility are taken into account, the configuration consisting of both reinforcing and connecting bars with straight end as anchorage detailing is recommended for the design of precast beam-column connections in case a central column removal scenario is assumed.

Behavior of Modified Strut-and-Tie Model (STM) on Concrete Beams

Reinforced concrete components are generally designed to withhold shear and bending based on the assumption at strain varies linearly in a section where the applied force is a combination of shear with bending, torsion, or normal forces. The behavior of shear failure in reinforced concrete beams is very different from that in flexural failure. Shear failure is brittle without warning in the form of significant deflection, resulting in diagonal cracks in the beam then the shear force mechanism will be contributed by an arching action where this action can provide a reserve capacity large enough for the beam to carry the load. Nonlinear analysis using the strut-and-tie method is particularly useful for shear-critical structures where classical beam theory is not valid due to significant shear deformations. Strut-and-Tie Model research which is applied to concrete (25 MPa), also uses the optimal configuration FEM software tool from Strut-and-Tie which leads to the efficiency of Strut-and-Tie. The results of the optimization and modification of the Strut-and-Tie Model on concrete will also be applied to the experimental models tested until they fail so that the optimal conditions for numerical models will be obtained.Based on the analysis result of element model using ANSYS computational assistance program, the ultimate flexural capacity of the beam model will increase depending on the used STM model and inclination angle (Φ), at the STM type 2 high < 1000 mm, inclination angle (Φ) 45° having a decrease in ultimate shear capacity (Vu) of 49,31% against type 1, at the STM model 3 high < 1000 mm, with inclination angle (Φ) 45° having an increase ultimate shear (Vu) of 4,14% against type 1. Stress pattern performed bottle shape in line with diagonal strut. Ductility capacity will be decreased at inclination angle <45° of 27,11%, at inclination angle >45° will be decreased of 55,67%,

Progressive collapse behaviour of earthquake-damaged interior precast concrete joints with headed bars and plastic hinge relocation

This study investigated progressive collapse behaviour of earthquake-damaged interior precast concrete (PC) joints with headed bars. The main objective was to quantify the impact of slight and moderate earthquake damage on their residual collapse resistance. The research began with a numerical investigation to understand the interaction between a 2D frame’s global response to seismic loading and its local response during a threat-independent progressive collapse event. Additionally, a separate set of numerical studies examined interior PC joints under cyclic loading to determine maximum drift ratio demands, yielding 2.5% for slightly and 3.5% for moderately damaged joints. Subsequently, an experimental programme under quasi-static loading conditions was conducted on five interior PC joints under cyclic loading, followed by progressive collapse resistance tests. Test results indicated that damaged joints exhibited flexural and catenary action during progressive collapse, but compressive arch action could not be mobilised due to residual cracks from the initial cyclic loading phase. Comparing damaged joints to fully intact ones from a companion study revealed deterioration in stiffness and deformation capacity during a subsequent progressive collapse, with degree of severity proportional to the extent of damage sustained in the cyclic loading phase. Relative to the intact joints without being subjected to cyclic loading, moderately damaged specimens exhibited a degradation of 63% in stiffness and 38% in deformation capacity, compared to slightly damaged specimens, which showed reductions of 38% in stiffness and 28% in deformation capacity. In contrast, strain hardening of steel bars in both slightly and moderately damaged specimens led to slightly greater collapse resistance than the intact joints. Additionally, failure mode shifted from ductile fracture to premature pull-through failure of headed bars in moderately damaged specimens. In this regard, in post-earthquake progressive collapse assessment, it is recommended to use maximum crack width thresholds of 0.2 to 1.0 mm for slight damage and 1.0 to 2.0 mm for moderate damage.

Progressive collapse resistance of precast concrete beam–column assemblies using dry connections under uniformly distributed loading condition

Improving the integrity of precast concrete (PC) frame structures using dry connections is essential for enhancing their robustness against progressive collapse. Therefore, three PC beam–column assemblies using different dry connections specially designed to ensure the connectivity were experimentally examined under progressive collapse scenarios. And a seven-point loading tree device was adopted to simulate the uniformly distributed loading conditions in practical engineering. The connection details were classified as follows: normal top-and-seat angle connection in TSA, strengthened top-and-seat angle connection in STSA, and strengthened top-and-seat angle with high ductility longitudinal reinforcements in the plastic regions in DSTSA. Under small deformations, STSA had the highest first peak load attributable to its strengthened joint connection. TSA obtained a lower load than that of STSA because of the low joint connection stiffness. Meanwhile, DSTSA achieved the lowest load among the three specimens because the smoother surface of the high-ductility reinforcements (compared with that of normal ones) weakened its bond to the concrete. However, under large deformations, the high ductility of the reinforcements ensured the specimen integrity; consequently, the largest final load was achieved in DSTSA. On the contrary, the high joint stiffness and normal reinforcements in STSA hindered the beam end rotation, and the steel angle failed early in TSA. As a result, the two connections failed to ensure the specimen integrity. To further shed light on the resistance mechanisms of beam–column assemblies under the uniformly distributed loading condition, an iteration-based model was developed to calculate the first peak load under the beam and compressive arch actions. The maximum prediction error achieved was 12%. Based on the model, the load contribution from the friction effect of the loading device was identified as 27%. And it was found that during the collapse, increasing reinforcement deformation region that might be induced by slippage between the concrete and reinforcements could lead to a continuous increase in the horizontal reaction force after the specimen reaching the first peak load.

ONE-WAY SLABS IN TRANSITION BETWEEN ONE-WAY SHEAR AND PUNCHING: EXPERIMENTS AND RECENT INSIGHTS FOR EVALUATION

Bridge deck slabs are members on which one-way reinforced concrete slabs are found frequently loaded by concentrated loads. Although the one-way shear failure mechanism has gathered more attention in the past years, both one-way shear and two-way shear mechanisms may be critical for such loading conditions. This paper addressed the ultimate capacity of thin one-way reinforced concrete slabs subjected to concentrated loads and yielding of the flexural reinforcement. In practice, the test setup studied was devised to represent short-span rural bridges frequently found in Brazil. The experimental program included 12 tests performed on 6 slabs applying the concentrated loads at varied positions. All tests started to fail by punching shear. Nevertheless, both one-way shear and punching shear cracks were observed at ultimate states after shear redistribution. The reinforcement yielding followed by excessive flexural cracking hampered the arching action activation for loads closer to the support. The comparison of experimental and calculated resistances using standard code-based expressions suggests that improvements in unitary shear capacity could be supported as a result of slabs' transverse load distribution capacity. Alternatively, increasing the effective shear width can help estimate one-way shear capacity for loads near to the support.

Analytical model of compressive arch action for one-way RC beams and two-way framed substructures under column removal scenarios

This paper proposes a direct analytical model to evaluate compressive arch action (CAA) of reinforced concrete (RC) beam-column sub-assemblages under middle column removal scenario (MCRS), incorporating bending curvature of the double-span beam, and different horizontal and rotational restraint conditions at the beam ends. Based on the proposed approach, the structural engineer can easily obtain the CAA peak capacity and the corresponding CAA displacement by hand calculations. Unlike the previous models in which the accuracy highly relies on pre-assumed CAA displacement, this prediction approach directly derives the CAA displacement and CAA capacity through force equilibrium, geometric relationship, compatibility and boundary conditions, incorporating various horizontal restraint conditions, span-to-depth ratio and section profile of the bridging beam. Comparison with existing test results in available literature indicates that this model not only gives good predictions of peak capacity, displacement and maximum axial beam force in CAA, but also incorporates the effect of horizontal restraint stiffness and working stress of compression reinforcement. Besides, a further simplified explicit model is proposed to enhance usability in practical design, and sensitive studies are conducted to study how the simplification affects the prediction accuracy of vertical CAA capacity and displacement. Thereafter, the proposed model is extended to substructures with orthogonal beams in X- and Y- directions to predict CAA capacity under different column removal scenarios such as interior, penultimate, edge and corner column removal cases.

Arching mechanism for large span flexible culverts with shallow soil covers

Soil-steel composite bridges (SSCBs) use the surrounding soil and the culvert’s flexible corrugated steel thin plates to support vertical loads above the culvert. Existing codes use empirical equations based on field measurements and full-scale tests for small and ordinary span SSCBs to estimate the arching process and how it distributes vertical stresses on the culvert walls. The empirical equations then compute the design straining actions. Recent developments in construction technology and urbanization have led to a significant increase in typical spans of SSCBs. This paper investigates large span SSCBs and the associated induced arching action using three-dimensional finite element analysis (FEA). The study compares the FEA findings of straining actions for large span SSCB case studies to the calculations of valid design codes. The comparison demonstrates that existing codes fail to predict the real arching mechanism and, consequently, the resulting straining actions. In addition, the FEA results illustrate how the arching mechanism varies as the span changes. Arching action is typically positive for relatively small spans but becomes negative as the span increases. Finally, results prove that current codes cannot accurately predict real arching, leading to inappropriate design straining actions. For large span SSCBs, these codes require modifications for the arching factors and the profile aspect ratio factors.

Effect of the arching action on the behavior of the RC precast concrete deep beams: comparison between several hybrid models

Effect of the arching action on the behavior of the RC precast concrete deep beams: comparison between several hybrid models

Cisalhamento induzido em vigas de concreto armado com agregado sintético

Abstract The increasing aluminum production demands larger volumes of bauxite residue (BR) to be stored in the Amazon region. There are millions of tons of waste without reuse but with high potential for use in civil construction as artifacts or components for concrete. Due to the significant consumption of coarse aggregates for concrete, there is the possibility of producing synthetic aggregate (SA) from bauxite residue, containing high levels of residue (70%, 80% and 90%), maintaining satisfactory levels of resistance and durability. To evaluate this new product, two beams were made with conventional aggregate (gravel) and the others with SA. For the evaluation of the shear strength, friezes were made to fix the failure surface, aiming to reduce the influences of the arch action on the shear strength, inducing the failure in the brittle section. The friezes presented inclinations of 30° or 45°, according to the calculation models of the Brazilian code for concrete structures. All beams were subjected to bending test until failure. The results showed that the SA has potential for use in reinforced concrete structures, presenting a similar performance to the conventional aggregate. The results also showed the preponderance of tensile when the a/d ratio increases, evidencing the greater contribution of the coarse aggregate with the increase of the strut inclination.

Whole-process analytical model on progressive collapse response of reinforced concrete structures under middle column loss

Since progressive collapse is essentially a dynamic process, the whole-process resistance evolution path is critical for a structure against progressive collapse. Previous analytical studies focus primarily on one particular phase of a single load transfer mechanism, such as compressive arch action (CAA) or catenary action (CA) capacity. This study develops a unified analytical model to evaluate the whole resistance-displacement curve of reinforced concrete (RC) structures. In the analytical model, compatibility, equilibrium condition, constitutive laws of concrete and reinforcing bars, and fracture of reinforcing bars are considered. To avoid complex iterations, curvature equations and combination schemes of cross-sectional forces are also established. The analytical model is verified against experimental resistances and axial forces of RC beam-column substructures measured in 24 tests, and it is subsequently utilized to illustrate the evolution of cross-sectional forces throughout the loading process. Furthermore, a sensitivity analysis based on the K-L entropy index is conducted to quantify the effects of different parameters on the progressive collapse resistance. The results show that the yield strength and diameter of reinforcing bars are vital to the whole resistance curves. The axial stiffness and beam depth primarily affect CAA capacity, while having a less significant impact on the CA capacity. Fracture displacement of reinforcing bars is the most influential parameter for CA capacity, suggesting the importance of considering the fracture of reinforcing bars in the analytical model.

Finite element analysis of progressive collapse resistance of precast concrete frame beam-column substructures with UHPC connections

Compared with reinforced concrete structure, precast concrete structure is prone to progressive collapse due to its poor continuity. The use of ultra-high performance concrete (UHPC) provides a feasible solution. To this end, investigate the influence of UHPC on the progressive collapse resistance of precast beam-column substructures, the finite element model of precast beam-column substructures with UHPC connections was established. The model was validated using available experimental data. Specifically, the cohesive-Coulomb friction model was used to simulate the interface behavior between precast concrete and cast-in-place concrete, and the metal ductile damage model was used to simulate rebar failure. The finite element simulation results show good agreement with experimental results, with an average error of less than 5 %. Additionally, five sets of full-scale analysis models were designed to analyze the effect of cast-in-place UHPC on the progressive collapse resistance of precast beam-column substructures. The results indicated that UHPC enhances the compressive arch action (CAA) capacity and catenary action (CA) capacity of precast beam-column substructures. Parametric analysis was conducted based on these models. The results indicated that the increase of UHPC strength grade can improve the CAA capacity of the structure, but reduce the CA capacity. Interface roughness has a certain effect on CAA capacity, but has no obvious effect on CA capacity. Finally, the accuracy of existing analytical models in predicting the CAA and CA capacity of UHPC-connected precast beam-column substructures is evaluated. The research results can provide reference for the design and application of precast concrete structures connected by UHPC.

Progressive collapse resistance of self-centering infilled precast concrete frame under side column removal scenario

In this study, the collapse experiment of a 1/2 scaled two-story and two-span self-centering precast concrete (PC) infilled frame specimen was carried out by quasi-static pushdown side column regime. The test results indicated that under side column removal scenario, the structural damage only occurred in the span adjacent to the failure column. The incline cracks in the infill wall showed a trend of developing from both sides to the middle portion during the test. Affected by the position of failure column, the initial stiffness and peak resistance of specimen under side column removal scenario were only 0.25 times and 0.44 times that of specimen under middle column removal. Further numerical simulation results indicated that the layout positions of infill wall, the initial prestress between beams and columns as well as the strength of bed joints had a greater effect on the vertical resistance of self-centering PC frames when side column failed. Moreover, the lateral restraints of the side columns on both sides could promote the development of compressive arch action (CAA) and catenary action (CA), and fully mobilized the tensile force of steel strands to undertake vertical load in the large deformation stage of the structure. Finally, a simplified analytical method was proposed to accurately predict the vertical resistance of self-centering PC frames in the CAA stage under side column removal scenario.