The Schwinger Model with Perfect Staggered Fermions

We construct and test a quasi-perfect lattice action for staggered fermions. The construction starts from free fermions, where we suggest a new blocking scheme, which leads to excellent locality of the perfect action. An adequate truncation preserves a high quality of the free action. An Abelian gauge field is inserted in d=2 by effectively tuning the couplings to a few short-ranged lattice paths, based on the behavior of topological zero modes. We simulate the Schwinger model with this action, applying a new variant of Hybrid Monte Carlo, which damps the computational overhead due to the non-standard couplings. We obtain a tiny ``pion'' mass down to very small \beta, while the ``\eta'' mass follows very closely the prediction of asymptotic scaling. The observation that even short-ranged quasi-perfect actions can yield strong improvement is most relevant in view of QCD.Comment: 30 pages, 16 figures. Following the referee's suggestions, we have incorporated the material of hep-lat/9803018 in this comprehensive pape

Alternative shear reinforcement for reinforced concrete flat slabs

This paper presents the first series of validation tests for a patented shear reinforcement system for reinforced concrete flat slabs. The system, called “Shearband,” consists of elongated thin steel strips punched with holes, which undulate into the slab from the top surface. The main advantages of the new reinforcement system are structural effectiveness, flexibility, simplicity, and speed of construction. Four reinforced concrete slabs were tested in a specially designed test rig. The slabs reinforced in shear exhibited ductile behavior after achieving their full flexural potential, thus proving the effectiveness of the new reinforcement. This paper reviews briefly existing types of shear reinforcement and identifies the need for more efficient and economic solutions. Details of the experimental setup and results are given, including strain and deflection measurements as well as photographs of sections through the slabs. Finally, comparisons are made with the ACI 318 and BS8110 code predictions, which confirm that the system enabled the slabs to avoid punching shear failure and achieve their flexural potential. In addition, both codes are shown to lead to conservative estimates of flexural and punching shear capacities of reinforced concrete slabs

Quenched hadron spectroscopy with improved staggered quark action

We investigate light hadron spectroscopy with an improved quenched staggered quark action. We compare the results obtained with an improved gauge plus an improved quark action, an improved gauge plus standard quark action, and the standard gauge plus standard quark action. Most of the improvement in the spectroscopy results is due to the improved gauge sector. However, the improved quark action substantially reduces violations of Lorentz invariance, as evidenced by the meson dispersion relations.Comment: New references adde

The quasi‐ductile resistance of compressed spun concrete beam‐columns

The expediency of reinforcing precast spun concrete members of annular cross sections reinforced by high‐strength steel bars is discussed. Test materials, mechanical properties, production and testing procedures of plain and rein‐forced spun concrete specimens are presented. The quasi‐ductile strength and strain features of concentrically and eccentrically loaded specimens are considered. The modelling of a bearing capacity of beam‐columns of annular cross sections is based on the concepts of bending with a concentrical force and compression with a bending moment. The comparison of modelling and test data of spun concrete beam‐columns is analysed. Santrauka Aptariamas didžiastipriais plieniniais strypais armuotu gamykliniu žiedinio skerspjūvio elementu iš centrifuguotojo betono tinkamumas. Pateiktos grynojo ir armuotojo centrifuguotojo betono bandiniu medžiagos, mechanines savybes, gamybos ir bandymo tvarka. Nagrinejamos centriškai ir ekscentriškai apkrautu bandiniu tartum stamantraus stiprumo ir deformaciju ypatybes. Žiedinio skerspjūvio sijiniu kolonu laikomajai galiai modeliuoti taikomos gniuždomojo lenkimo ir lenkiamojo gniuždymo sampratos. Analizuojami sijiniu kolonu iš centrifuguotojo betono modeliavimo ir bandymo duomenys. First Published Online: 24 Jun 2011 Reikšminiai žodžiai: centrifuguotasis betonas, didžiastipris plienas, žiedinio skerspjūvio elementai, ekscentrinis apkrovimas, gniuždymo bandyma