Limited Deformability Design of High-Strength Concrete Beams in Low to Moderate Seismicity Regions / Stipriojo Betono Sijų Ribinio Deformatyvumo Skaičiavimas Žemo Ir Vidutinio Seismingumo Regionuose

Abstract

In the design of reinforced concrete (RC) beams located in low-moderate seismicity regions, adequate flexural deformability apart from flexural strength to cater for the imposed seismic demand should be designed. As per the existing RC design codes, this is achieved by restricting the maximum neutral axis depth or tension steel ratio, or limiting the minimum confining steel. However, these deemed-to-satisfy rules were derived many years ago based on normal-strength concrete and steel, which would impair the deformability when applied directly to RC beams made of high-strength materials. To resolve the problem, a new design method based on a prescribed deformability is advocated. In this study, the authors proposed that instead of complying with the deemed-to-satisfy rules, a consistent deformability derived based on the design requirements of Eurocode 2 should be provided to all RC beams located in low-moderate seismicity regions. Using the theoretical formulas developed previously by the authors, two different sets of design values expressed in terms of maximum tension steel ratio and neutral axis to beam effective depths for different concrete and steel yield strengths are evaluated. Finally, simplified guidelines for designing RC beams satisfying the proposed deformability requirement are developed for practical design application. Santrauka Mažo ir vidutinio seismingumo regionuose projektuojant seisminių apkrovų veikiamas gelžbetonines sijas turi būti užtikrinta ne tik jų laikomoji galia, bet ir tinkamas deformatyvumas. Pagal šiuo metu galiojančias gelžbetoninių konstrukcijų projektavimo normas tai pasiekiama ribojant didžiausiąjį skerspjūvio aukštį, tempiamosios zonos armavimo procentą arba ribojant mažiausią armatūros kiekį. Tačiau šios konstravimo taisyklės buvo sukurtos prieš daugelį metų ir skirtos elementams iš normalaus stiprio betono ir armatūros. Jas tiesiogiai taikant gelžbetoninėms sijoms, pagamintoms iš stipriųjų medžiagų, gaunamas sumažintos deformacijos. Šiais problemai spręsti siūlomas naujas projektavimo metodas, paremtas nustatytu deformatyvumu. Autoriai siūlo mažo ir vidutinio seismingumo regionuose visas gelžbetonines sijas projektuoti pasirenkant deformacijas pagal ”Eurokode 2“ pateiktus deformatyvumo reikalavimus. Pagal anksčiau autorių gautas teorines formules skirtingiems betono ir plieno stipriams pateiktos dvi atskiros skaičiuojamųjų rodiklių grupės išreikštos maksimaliu tempiamosios zonos armavimo koeficientu ir efektyviuoju sijos skerspjūvio aukščiu. Praktiniam taikymui sukurtos supaprastintos gelžbetoninių sijų projektavimo rekomendacijos, atitinkančios deformatyvumo reikalavimus.

Plastic Rotation Capacity of Lightweight-Aggregate Concrete Beams

“…However, the flexural behaviour of LWAC beams, including NS and HS concrete, still continues to be studied because several requirements of codes of practice continue to be based on the experimental results of NWAC beams. Recent papers about this subject, including HS LWAC beams, can be found in the literature (Liu et al 2006;Jung et al 2007;Sin et al 2010;Ho, Zhou 2011;Bernardo et al 2014). Although some proposals for the extension of European codes of practice to include LWAC, including HS concrete, have been reported (Faust 2000;Fib 2000), they are still not fully incorporated.…”

Flexural Ductility of Lightweight-Aggregate Concrete Beams

“…Recent papers about this subject, including HS LWAC beams, can be found in the literature (for example, Liu et al 2006;Jung et al 2007;Sin et al 2010;Arslan, Cihanli 2010;Ho, Zhou 2011). This shows that several aspects about flexural performance of LWAC beams are not fully clarified.…”

Incorporation of Rubber-Steel Bearing Isolation in Multi-Storey Muilding

“…The finite element modelling has been developed and the analyses of multi-storey structure are performed by sophisticated finite element code SAP 2000 (CSI 2004). Static analysis and free vibration analysis (Betti, Vignoli 2011;Ho, Zhou 2011;Jameel et al 2012;Patil, Jangid 2011) were performed along with dynamic analysis in frequency domain. The acceleration excitation behaviours for fixed and isolated buildings were assessed with the displacement patterns at different levels as well.…”