RC Coupling Beams with High-Strength Steel Bars: Summary of Test Results

The use of high-strength steel bars in reinforced concrete coupling beams is expected to reduce reinforcement congestion. A series of tests was conducted to investigate the effects of high-strength reinforcement on coupling beam behavior. This report summarizes the test program and test results. Eleven large-scale coupling beam specimens were tested under fully reversed cyclic displacements of increasing magnitude. The main variables of the test program included: yield stress of the primary longitudinal reinforcement (Grade 80, Grade 100, and Grade 120 [550, 690, and 830]), span-to-depth (aspect) ratio (1.5, 2.5, and 3.5), and layout of the primary longitudinal reinforcement (diagonal [D] and parallel [P]). All beams had the same nominal concrete compressive strength (8,000 psi [55 MPa]) and cross-sectional dimensions (12 by 18 in. [305 by 457 mm]). Beams were designed for a target shear strength based on the upper limits specified in ACI 318-14. All transverse reinforcement was Grade 80 (550), except one specimen that had Grade 120 (830) transverse reinforcement. The test program is documented by presenting the details of specimen construction, test setup, instrumentation, and loading protocol. Documentation of test results include material properties and cyclic force-deformation response.Charles Pankow FoundationConcrete Research CouncilConcrete Reinforcing Steel Institut

Reinforced Concrete Coupling Beams with High-Strength Steel Bars

The use of high-strength steel bars in reinforced concrete coupling beams has the potential to reduce reinforcement congestion and support more efficient design and construction methods. A series of tests was conducted to investigate the effects of high-strength reinforcement on coupling beam behavior. Eleven large-scale coupling beam specimens were tested under fully reversed cyclic displacements of increasing magnitude. The main variables of the test program included: yield stress of the primary longitudinal reinforcement (Grades 80, 100, and 120 [550, 690, and 830]), span-to-depth (aspect) ratio (1.5, 2.5, and 3.5), and layout of the primary longitudinal reinforcement (diagonal [D] and parallel [P]). All beams had the same nominal concrete compressive strength (8,000 psi [55 MPa]) and cross-sectional dimensions (12 by 18 in. [310 by 460 mm]). Beams were designed for target shear stresses of 8√f’c psi (0.67√f’c) for D-type beams and 6√f’c psi (0.5√f’c) for P- type beams. Transverse reinforcement was Grade 80 (550) in all but one beam, which had Grade 120 (830) reinforcement. The test program is documented by presenting the details of specimen construction, test setup, instrumentation, and loading protocol. Documentation of test data includes material properties, cyclic force-deformation response, progression of damage, calculated and measured strengths, initial stiffness, and measured reinforcement strains. Analysis of test data includes hysteretic energy, changes in beam length and depth, components of chord rotation, and the development of an equation for estimating chord rotation capacity.Charles Pankow FoundationACI Foundation’s Concrete Research CouncilConcrete Reinforcing Steel Institut

High-Strength Steel Bars in Earthquake-Resistant T-Shaped Concrete Walls

The object of this study was to determine experimentally the influence of selected reinforcing steel mechanical properties on wall deformation capacity. Four large-scale T-shaped reinforced concrete wall specimens with different types of reinforcement were subjected to reversed cyclic displacements. The primary variables were the yield strength () and the tensile-to-yield strength ratio (/) of the reinforcing bars. The study also aimed to identify the minimum uniform elongation () and fracture elongation () required of high-strength reinforcement for use in earthquake-resistant concrete structures. Test data are presented from four walls, T1 with conventional Grade 60 (420) reinforcement and T2, T3, and T4 with high-strength Grade 100 (690) reinforcement. The flexural reinforcement consisted of No. 6 (19) bars inside confined boundary elements and No. 4 (13) bars elsewhere. Confining reinforcement in boundary elements consisted of No. 3 (10) hoops and crossties of the same grade as the flexural reinforcement. Wall T1 had / of 1.34 and 1.39 for the No. 6 (19) and No. 4 (13) bars, respectively. Walls with Grade 100 (690) reinforcement had / of 1.15 and 1.10 for T2, 1.23 and 1.21 for T3, and 1.36 and 1.20 for T4. All walls were loaded with a shear span-to-depth ratio of 3 and had the same nominal dimensions and concrete compressive strength (8 ksi or 55 MPa). Axial load was limited to the self-weight of the wall and testing apparatus. The walls were designed to have nearly the same nominal flexural strength. Flexural yielding controlled the lateral strength of the walls, inducing an average shear stress up to 3.5√′, psi (0.29√′, MPa). To ensure large tensile strain demands in one of the loading directions, the neutral axis depth at nominal flexural strength did not exceed the thickness of the flange. Design of the walls complied with ACI Building Code (ACI 318-14) requirements for special structural walls with additional detailing requirements applied based on ATC 115. Walls designed for a target flexural strength using Grade 60 (420) or Grade 100 (690) reinforcement, with similar / for the primary flexural reinforcement, had similar strength and deformation capacity (defined as the drift cycle completed before a 20% loss of lateral strength). The limited test data indicate that walls with low axial force and reinforcement that satisfies tensile-to-yield strength ratio (/) ≥ 1.2, uniform elongation () ≥ 6%, and fracture elongation () ≥ 10% exhibit a minimum drift ratio capacity of 3%. Walls T1, T2, T3, and T4 exhibited drift ratio capacities of 3.7, 1.8, 3.0, and 3.9%, respectively. Moment-curvature analyses were conducted to evaluate the use of the plastic hinge model for estimating the deformation capacity of the walls and the maximum strain demands. The use of the plastic hinge model was conservative for estimating wall deformation capacity with simple rules for the plastic hinge length depending on whether deformations due to shear and strain penetration are considered. However, the plastic hinge model did not consistently provide conservative estimates of the maximum strain demands.Charles Pankow FoundationConcrete Research Council, American Concrete Institute Foundatio

Search for resonances in the mass spectrum of muon pairs produced in association with b quark jets in proton-proton collisions at root 8 and 13 TeV

A search for resonances in the mass range 12-70 GeV produced in association with a b quark jet and a second jet, and decaying to a muon pair, is reported. The analysis is based on data from proton-proton collisions at center-of-mass energies of 8 and 13 TeV, collected with the CMS detector at the LHC and corresponding to integrated luminosities of 19.7 and 35.9 fb(-1), respectively. The search is carried out in two mutually exclusive event categories. Events in the first category are required to have a b quark jet in the central region (|| 2.4) and at least one jet in the forward region (|| > 2.4). Events in the second category are required to have two jets in the central region, at least one of which is identified as a b quark jet, no jets in the forward region, and low missing transverse momentum. An excess of events above the background near a dimuon mass of 28 GeV is observed in the 8 TeV data, corresponding to local significances of 4.2 and 2.9 standard deviations for the first and second event categories, respectively. A similar analysis conducted with the 13 TeV data results in a mild excess over the background in the first event category corresponding to a local significance of 2.0 standard deviations, while the second category results in a 1.4 standard deviation deficit. The fiducial cross section measurements and 95% confidence level upper limits on those for a resonance consistent with the 8 TeV excess are provided at both collision energies

Search for top squark pair production in pp collisions at root s=13 TeV using single lepton events

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Search for direct production of supersymmetric partners of the top quark in the all-jets final state in proton-proton collisions at root s=13 TeV

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Pseudorapidity distributions of charged hadrons in xenon-xenon collisions at root S-NN=5.44 TeV

Measurements of the pseudorapidity distributions of charged hadrons produced in xenon-xenon collisions at a nucleon-nucleon centre-of-mass energy of root S-NN = 5.44 TeV are presented. The measurements are based on data collected by the CMS experiment at the LHC. The yield of primary charged hadrons produced in xenon-xenon collisions in the pseudorapidity range vertical bar eta vertical bar <3.2 is determined using the silicon pixel detector in the CMS tracking system. For the 5% most central collisions, the chargedhadron pseudorapidity density in the midrapidity region vertical bar eta vertical bar <0.5 is found to be 1 187 +/- 36 (syst), with a negligible statistical uncertainty. The rapidity distribution of charged hadrons is also presented in the range vertical bar y vertical bar <3.2 and is found to be independent of rapidity around y = 0. Existing Monte-Carlo event generators are unable to simultaneously describe both results. Comparisons of charged-hadron multiplicities between xenon-xenon and lead-lead collisions at similar collision energies show that particle production at midrapidity is strongly dependent on the collision geometry in addition to the system size and collision energy. (C) 2019 The Author(s). Published by Elsevier B.V.Peer reviewe

Search for pair production of second-generation leptoquarks at root s=13 TeV

A search for pair production of second-generation leptoquarks is performed using proton-proton collision data collected at √s=13  TeV in 2016 with the CMS detector at the CERN LHC, corresponding to an integrated luminosity of 35.9  fb−1. Final states with two muons and two jets, or with one muon, two jets, and missing transverse momentum are considered. Second-generation scalar leptoquarks with masses less than 1530(1285) GeV are excluded for β=1.0(0.5), where β is the branching fraction for the decay of a leptoquark to a charged lepton and a quark. The results of the search are also interpreted as limits on the pair production of long-lived top squarks in an R-parity violating supersymmetry model that has a final state with two muons and two jets. These limits represent the most stringent limits to date on these models.Peer reviewe

Charged-particle angular correlations in XeXe collisions at root s(NN)=5.44 TeV

Azimuthal correlations of charged particles in xenon-xenon collisions at a center-of-mass energy per nucleon pair of root s(NN) = 5.44 TeV are studied. The data were collected by the CMS experiment at the LHC with a total integrated luminosity of 3.42 mu b(-1). The collective motion of the system formed in the collision is parametrized by a Fourier expansion of the azimuthal particle density distribution. The azimuthal anisotropy coefficients v(2), v(3), and v(4) are obtained by the scalar-product, two-particle correlation, and multiparticle correlation methods. Within a hydrodynamic picture, these methods have different sensitivities to noncollective and fluctuation effects. The dependence of the Fourier coefficients on the size of the colliding system is explored by comparing the xenon-xenon results with equivalent lead-lead data. Model calculations that include initial-state fluctuation effects are also compared to the experimental results. The observed angular correlations provide new constraints on the hydrodynamic description of heavy ion collisions.Peer reviewe