[26년 3회 대비] 건축기사 실기 443제 Part 1 (1~220제) | 2025~2017년 기출 중복제외 | 올인원 총정리

Overview

The video is a rapid review of 220 construction-engineering practical exam questions. The presenter groups recurring concepts into short rules, formulas, and memory cues across construction methods, concrete, structural design, scheduling, earthwork, and quality control.

A recurring study strategy is to identify the key distinction in each question—for example, where mortar is applied, which load path is involved, or whether a value is total, free, or interfering float—and then memorize the relevant sequence or formula.

Main Concepts and Lessons

1. Construction Methods, Materials, and Site Practice

• Waterproofing masonry walls: The three methods described are cement-mortar waterproofing, silicate-based waterproof coating, and water-repellent coating. The memory cue is: mortar densifies, silicate material fills pores, and water repellent makes water bead off the surface.
• Private investment method — BTL: Build–Transfer–Lease. The private party builds the facility, transfers ownership to the government, and recovers its investment by leasing the facility to the government.
• Steel grade notation: In SM355, SM identifies a structural steel grade used for welded construction; 355 denotes yield strength in MPa, not tensile strength.
• Camber and topping concrete: Camber is an intentional upward bend, or its amount, used to compensate for expected deflection. Topping concrete is cast over a floor slab to adjust its surface or height and help distribute loads.
• Rebar installation sequence: Work from the foundation upward, then install horizontal members: foundation → columns → walls → beams → slabs.
• Tile attachment and joints:
  • Pressed attachment: Mortar is placed on the back of each tile, which is pressed onto the base.
  • Adhesive attachment: Mortar is spread on the base, and tiles are tapped or rubbed into place.
  • Expansion joints: Placed where movement or cracking is anticipated so deformation can be absorbed.
• Concrete formwork removal: The required waiting period increases as temperature falls and as the cement type gains strength more slowly. The lecture gives the pattern 2/4/5 days in warmer conditions and 3/6/8 days in cooler conditions, ordered from rapid-hardening to slower-hardening cement.
• Stone polishing: Progress from coarse to fine: rough grinding → wet grinding → regular grinding → fine grinding.
• Accumulated temperature: For early-strength concrete, temperature accumulated over the curing period can be used to assess strength development and help judge formwork-removal timing.
• Ready-mix concrete at delivery: Check slump, slump flow, air content, and concrete temperature.
• Choosing a ready-mix plant: Check travel and delivery time, the plant’s production capacity, and whether enough mixer trucks are available for continuous placement.
• Concrete placement interval: The lecture cites a maximum interval of 150 minutes at 25°C or below and 120 minutes above 25°C to reduce the risk of a cold joint.
• Cold-weather concreting: The lecture identifies a daily average temperature below 4°C as a cold-weather concern. It recommends keeping the water–cement ratio at or below 60% and using suitable air-entraining admixtures.
• Concrete spalling in fire: Rapid heating can turn internal moisture to vapor. Pressure builds and may exceed the concrete’s resistance, causing explosive surface spalling.
• Alkali–aggregate reaction prevention: Reduce alkali content, avoid reactive aggregates, use suitable supplementary materials, and limit moisture penetration.
• Mass-concrete temperature cracking: Reduce cement content, use low-heat cement where appropriate, pre-cool materials or concrete, and use pipe cooling.
• Curing and shrinkage joints:
  • A control joint deliberately creates a weakened section to guide shrinkage cracks.
  • A construction joint is planned.
  • A cold joint occurs when placement is delayed and the earlier concrete begins to harden before the next placement.
• Temporary works and safety:
  • Fall-prevention railings include a midrail, posts, and toe board.
  • A fall-protection net catches falling objects or people; a toe board helps prevent materials from sliding off platform edges.
  • Anchor bolts may be fixed before concrete placement, adjusted during construction, or installed afterward.
  • Wet fireproofing methods include casting, spraying, plastering, and masonry.
  • A hanging scaffold is suspended from above; a low horse scaffold is supported by short legs.
  • Jack supports are temporary supports left after formwork removal, particularly beneath slab and beam midspans, to limit cracking from loads and vehicle vibration.
• Other construction terms and methods:
  • Slurry-wall stabilizing fluid helps keep excavation walls stable, restrict groundwater inflow, and separate and carry away soil.
  • Earth anchors support retaining walls from behind, leaving more room inside an excavation. Interference with adjacent property or utilities and required consent must be considered.
  • Shotcrete is concrete or mortar sprayed with compressed air. It can avoid formwork, but may create dust and rebound, and the finished surface can be rough or crack-prone.
  • Top-down construction can use an early first-floor slab as a work platform and material-storage area.
  • Fast-track construction overlaps design and construction by starting work on completed portions of the design.
  • Trench-cut excavation starts at the perimeter and then excavates the center; island-cut starts at the center and then works outward.
  • Micropiles are small-diameter piles suited to restricted sites and work where vibration and noise need to be limited.
  • Sand-drain methods use sand columns to help drain water from soft clay and accelerate consolidation.
  • Wood is naturally dried by stacking it to allow gradual ventilation. The lecture emphasizes low equipment cost and fewer rapid-drying defects.
• Specification, contracts, and planning:
  • The lecture presents the design-document precedence order as construction specifications, drawings, special specifications, standard specifications, and then the construction cost estimate.
  • Environmental plans cover recycling construction waste and industrial by-products, reducing greenhouse-gas emissions, and conserving natural resources.
  • A quality-management plan includes project information, quality policy and objectives, site organization, and document management.
  • A safety-management plan and a hazardous-risk-prevention plan are distinguished by the laws and subject matter they address.
  • LCC covers costs across a building’s life cycle, from planning and design through construction, operation, maintenance, demolition, and disposal.
  • VE seeks better value by maintaining required performance and quality while reducing cost.

2. Concrete, Masonry, and Materials Testing

• Concrete mix terminology:
  • The water–cement ratio uses the mass of cement as its denominator.
  • The water–binder ratio uses cement plus supplementary cementitious materials or admixtures as its denominator.
  • The lecture distinguishes saturated-surface-dry aggregate, absolutely dry lightweight aggregate, and water–binder ratio in mix-design questions.
• Ready-mix specification notation: The examples interpret the figures as concrete type, maximum aggregate size, nominal strength, and slump. A typical notation gives aggregate size in millimetres, strength in MPa, and slump in millimetres.
• Entrained air: Small, intentionally introduced air bubbles improve workability, reduce segregation and bleeding, and improve freeze–thaw resistance.

• Concrete strength tests:

  • Split tensile strength: Test by laying a cylindrical specimen on its side and loading it until it splits. The formula is:

  Split tensile strength = 2P / (πDL)

  where P is maximum load, D is diameter, and L is specimen length.

  • Compressive strength: Maximum failure load divided by specimen cross-sectional area. Convert kN to N when calculating MPa.
  • Nondestructive strength-estimation methods: Rebound-hammer testing, ultrasonic pulse velocity, and pull-out testing.
  • Schmidt-hammer readings: May need correction for impact direction, concrete stress state, moisture condition, and age.
  • Ready-mix aggregate moisture: Absorption is the water held inside aggregate pores in a saturated-surface-dry condition; moisture content includes internal and surface water.
  • Concrete block and brick quantities: Calculate wall area, multiply by the specified number of units per square metre, then include the stated allowance for breakage or waste. The lecture cites a 5% allowance for cement bricks and 3% for red bricks in its examples.
  • Masonry rules and patterns: The lecture reviews joint width, daily construction height, and reinforcement at brick or block intersections, as well as patterns such as English bond, Flemish bond, herringbone, and perforated decorative brickwork.
  • Other material terms:
  • Low-E glass uses a low-emissivity coating to reduce heat transfer while admitting visible light.
  • Insulated spacers maintain the gap between panes.
  • Laminated glass contains an interlayer that helps hold fragments together if it breaks.

3. Structural Design and Analysis

• Seismic systems:
  • A bearing-wall system resists vertical and lateral loads through walls.
  • A moment frame resists loads through beam–column joints and frame action.
  • Seismic-force-resisting systems resist earthquake forces directly; energy-dissipating systems absorb energy; seismic-isolation systems reduce transmission of ground motion into the building.
  • Eccentric placement of a core or shear wall relative to the mass and stiffness centers can cause torsion during an earthquake.
  • The lecture distinguishes the response-modification factor, system overstrength factor, and displacement-amplification factor.
• Foundation and ground concerns: The lecture covers frost protection, heaving, piping, boiling, buoyancy, differential settlement, and soil improvement. Prevention methods include placing foundations below the frost depth, using insulation, replacing frost-susceptible soil, drainage or groundwater lowering, increasing structural weight, and using anchors or piles where appropriate.
• Structural terms and components: Topics include transfer beams in pilotis buildings, anchor bolts, base plates, non-shrink grout, embedded composite columns, column shortening, lamellar tearing, weld scallops, and reinforcement ties. The examples stress identifying what each component does and where it transfers load.
• Welds and bolted connections:
  • Fillet welds: Effective length can be found by dividing the factored load by the design strength per unit length; use the weld-metal strength and effective throat thickness.
  • High-strength friction-bolt connections: The lecture uses a minimum slip coefficient of 0.5 and describes field bolt tension as 10% above design bolt tension.
  • Bolt-layout terms: Pitch is the spacing between bolt centers along a line; a gauge line connects bolt centers; gauge is the distance between adjacent gauge lines.
  • Weld inspection methods: Radiographic and ultrasonic tests detect internal defects; magnetic-particle and penetrant tests detect surface defects.
  • Lamellar tearing is associated with through-thickness tensile restraint during welding; a scallop is a cutout that helps avoid weld overlap and repeated heating.
• Common calculation approaches:
  • Weld design: Determine factored load → effective throat → design resistance per unit length → required effective length.
  • Earthwork: Distinguish loose, bank, and compacted volumes. The lecture uses swell and shrinkage factors and emphasizes applying the conversion in the correct direction.
  • Excavation, backfill, and disposal: Calculate the excavation volume, subtract the underground structure to obtain backfill, and apply the relevant conversion factor to obtain spoil disposal.
  • Section properties: Split irregular sections into simple shapes and use the parallel-axis theorem: add each part’s own second moment of area to its area multiplied by the square of its distance from the reference axis.
  • Columns: Effective buckling length equals the effective-length factor multiplied by actual length. Use the weaker-axis second moment for Euler buckling calculations; the effective-length factor depends on end restraint.
  • Deflection and deformation: Use the appropriate elastic relation, keeping force, length, area, and modulus units consistent. For axial deformation, the lecture uses PL/AE.
  • T-beams and slabs: Identify effective flange-width limits, the neutral axis, the effective depth, and whether a slab acts in one or two directions. The lecture uses a span ratio of 2 as the one-way/two-way distinction.
  • Punching shear: Possible strengthening measures include increasing slab thickness, enlarging the critical section, adding shear reinforcement, or using a shear head.
  • Load combinations and strength checks: Calculate the relevant load effects and compare candidate combinations; the lecture notes a seismic load factor of 1.0 in the cited combination.
  • Foundation eccentric loading: Combine direct stress from axial load with bending stress due to eccentricity; the maximum compression occurs on the side toward the eccentricity.
  • Other structural topics: The video also reviews crack-control moments, long-term deflection and creep, truss determinacy, beam reaction forces and diagrams, and load transfer through slabs, beams, columns, and foundations.

4. Scheduling, Quantity Surveying, and Construction Management

• Network scheduling method:
  1. Draw activities and precedence relationships.
  2. Calculate early times in a forward pass, using the largest incoming value.
  3. Calculate late times in a backward pass, using the smallest outgoing value.
  4. Identify the critical path as the path with zero total float; its duration is the project duration.
  5. Distinguish total float, free float, and interfering float. The lecture gives interfering float as total float minus free float.
  6. Treat dummy activities as links that show dependency, not as work with duration.
• Project duration reduction (“crashing”): Calculate the cost slope for each activity, shorten the least-cost activity on the critical path first, and recalculate the network. If multiple paths become critical, shorten activities on all affected paths together. Do not shorten an activity beyond its available crash limit.
• PERT and activity representation: PERT estimates duration from optimistic, most likely, and pessimistic times. PDM represents activities as nodes; ADM represents activities as arrows.
• Line of Balance: For repetitive work such as high-rise floors, graph time against floors and use the slope of each crew’s line to compare progress and productivity.
• Quantity calculation habits: Convert dimensions to consistent units before computing volume, area, weight, or material quantities. Apply waste allowances only after calculating the net quantity. For labor, multiply area by labor per unit area to obtain total labor, then divide by crew size to find working days.
• Other management topics: The video explains local-restriction competitive bidding, joint contracting and “paper” participation, comprehensive evaluation bidding, subcontracting-plan bidding, alternative-proposal bidding, and reimbursement-ratio contracts.

Speakers and Sources Featured

• Speaker: One presenter, who introduces himself as David and narrates the lesson. No other speakers are heard in the subtitles.
• Channel/source: 기출연구소 답이요 (“Past Exam Questions Research Institute,” as rendered in the subtitles).
• Study references mentioned: Construction standard specifications, building structural standards, Korean industrial standards, and construction- and occupational-safety-related regulations. These are referred to as exam or technical standards, not as additional speakers.