Composite construction

• Composite construction
• Portal Frames
• • introduce
  • materials
  • types
  • theory
  • connections
  • 3D model
  • conventional framed- building
  • • slab
• Construction of framed structures
• • construction drawings
  • ==**operation process**==
• Summary

Composite construction

• . construction is basically an assembly of in-situ(现场) and
  ex-situ(非现场) structural and non-structural elements;

• various terminologies(术语) have been coined to describe ex-situ
  elements e.g. prefab(预制), pre-assemly(预装配), modularization(模块化);

• drivers include:

• tight project shedule;
  2. design requirements-clear span(跨度), limited dimensions;
  3. quality control;

• cost;

• however, there are less flexible and often present tight
  tolerances(精度) for constrction;

• civil engineering projects can be classified under:

• substructure(底部构造) i.e foundations and basements;

• superstructure(上层构造) i.e. frame and cladding;

• services

• the substructure is invariably in- situ but the superstructure may be
  wholly prefabricated modular units or a composite

• this lecture focuses on composite portal frame(综合门户框架) and skeletal construction(骨架)

Portal Frames

（门式框架)

introduce

portal frames are rise dtructures based on the skeletal concept;
structurally, portal frame comprise foundation(in-situ concrete), column(preformed timber, steel or concrete) and rafters for the roof;
members connected to give a continuous rigid structure(刚性结构);

materials

• haunches(加腋) provided to enhance the stiffness of the frame;
• large clear spans;
• stell, concrete, timber;
  
  

types

• pitched roof portal frame(坡口构架);
• mansard portal frame(双重斜坡的门户框架);
• propped portal frame(支撑框架);
• cellular portal frame(蜂窝门框);
  

theory

bending moment & deflection proportional to span

connections

3D model

conventional framed- building

（传统建筑物框架）

• base on the skeletal concept of desugn- load paths: roof/slab—>
  beams—>column—>foundation
• often a choice between timber/ concrete/ steel;
• analysed in terms of(依据) strength per unit weight; cost per unit
  weight; construction; sustainability etc;
• foundation in-situ, columns and beams tend to be precast concrete or
  steel;

slab

slab can be:

• precast concrete hollowcore;
• precast double tees;
• waffle or ribbed slabs;
• metal decking;
• precast soild slab;
  

Construction of framed structures

1. design and construction based on a grid–usually a structural
   grid(结构网格);
2. design philosophy(设计理念) can be based on a permissible stress or limit
   state depending on applicable norm(规范)–BS or Eurcode;
3. design output- a set of construction drawings(一套设计图纸) including-
   general arrangement, elevations and sections;
4. on site, contractor sets out–coordinates, bearings and distances,
   offsets from a baseline;
5. connection depends on the design; welding(焊接) or bolting(螺栓);

construction drawings

general arrangement**😗*

north elevation**😗*

plan and section through foundation**😗*

operation process

1. clear site(清理场地)
2. set out footings(确定放置位置)
3. excavate pits, allow working space(挖坑，留出工作空间)
4. compact bottoms of excavations(压实底部)
5. lay blinding/bedding layer(铺垫层)
   
6. place spacers & mesh(铺垫块和钢筋网)
7. set out positions of anchor bolts(设定地脚螺栓的位置)
8. fix hold down/ anchor bolts(固定地脚螺栓)
9. fix pockets for horizontal adjustment
   
10. pre-formed gusset plates installed to tie anchor bolts(成品扣板安装到地脚螺栓上)
11. exact gusset positions marked and secured(确定扣板位置并固定)
12. cast concrete(浇灌混凝土)
13. afetr specified curing, remove formwork and backfill(固化后，拆除膜壳并回填)
    .
14. install stanchions/columns by bolting–lose bolting intially(通过螺栓安装支柱)
15. adjustment horizontally using pockets & vertically by packing the base(调整使支柱水平且垂直)
    
16. progress to rafter installation(安装椽)
17. final tightening upon satisfactory horizontal and verticality checks(水平，竖直检查确认后紧固)
18. grount all pocket(重复操作)

Summary

• portal frame for large spanning unobstructed spaces(大跨度，无障碍);
• hinges(铰链) introduced to control moments;
• members prefabricated(工件预制), preparatory works essential;
• design must consider possible tolerances(精度), and construction must
  aim to achieve these;